Mac OS X has been around for more than 10 years. You’d think that by now there wouldn’t be much room for improvement. But this latest version – 10.7 if you’re counting – would prove you wrong.

Apple says Lion adds 250 new features to OS X. Many are borrowed from iOS. Some are tailor-made for new Mac users. And others improve (or fix) features that have been around for a while. Do these changes make Lion a must-have for you?

To help you answer that question, we’ve assembled summaries of the most important new features, and Macworld’s Jason Snell has written an extensive review. Read on and decide for yourself.

Mission Control

Apple bills Mission Control as a kind of central command for your Mac – a quick, organised overview of everything that’s currently open on your computer. You can activate it in a number of ways – swiping upwards with three fingers (by default) on a trackpad, clicking on the Mission Control icon in the Dock, pressing the Exposé hotkey on your Mac’s keyboard, pressing a keyboard shortcut, or moving your cursor to a hot corner (the last two are configurable in the Mission Control system preferences).

You’ll then see an Exposé-like bird’s-eye view of your open windows, organised in stacks by application. Each stack is labelled with the name of the application and its icon. Clicking on an application’s icon brings the application and all of its windows to the foreground; you can also click an individual window to bring it to the front.

Above those windows you see a horizontal list of your open desktops (formerly known as Spaces). In previous versions of OS X, you could disable those virtual desktops if you didn’t want to use them; not any more.

By default you have two spaces: Dashboard and desktop. To create a new one, drag an application toward the top of the screen. A picture of your desktop will appear in the upper right corner; drop what you’re dragging on it, and you have a new desktop.

Navigating spaces

Trackpad users can move from one space to another with a sideways swipe (using three or four fingers) in Mission Control or on a standard desktop. You can also switch by clicking on one of your spaces in Mission Control. If you want to move a window or an application from one space to another, you switch to the first space in Mission Control and then drag whatever you want to move to the second. Strangely, you can’t rearrange or rename spaces. Another change from Spaces in Snow Leopard is that they now appear only in that horizontal line instead of in two-dimensional grids.

If you’ve been a fan of Exposé, don’t fret: its other features – displaying all windows in an application and exposing your desktop – are still there.

Launchpad

Launchpad is the clearest example of the ‘iOS-ification’ of Mac OS X. It’s as if Apple copied the interface from an iPhone and pasted it onto the Mac.

You open Launchpad in a number of ways: clicking on its spaceship icon in the Applications folder or on the Dock; pinching three or four fingers together on a trackpad; or moving the cursor to a hot corner.

The applications that come with OS X are on the first Launchpad screen, with third-party applications relegated to subsequent screens. You can switch between screens with a two-finger sideways swipe on a trackpad; by using the left and right arrow keys on the keyboard; or by clicking the little dots at the bottom that represent your Launchpad screens.

Launching and organising

As in iOS, you launch an application in Launchpad by clicking on it and rearrange applications by dragging them. You don’t need to click and hold on one to make it start jiggling before you move it (as you do in iOS), but you can if you prefer. To delete an application (something you can’t do to any of Apple’s own programs), click and hold and then tap the X in the application icon’s top-left corner.

Launchpad also sports iOS-style folders for organising your applications. As on your iPhone or iPad, you create new folders by dragging one icon on top of another. You can’t have a folder with one application in it; the folder disappears when there’s only one left.

New programs downloaded from the Mac App Store go directly into Launchpad, as do any you drag into the Applications folder. Unfortunately, there’s no easy way to order applications other than by dragging them from one place to another. There’s no option to sort them alphabetically by name, for example.

Awkwardly, the folders you create in Launchpad aren’t reflected in the Applications folder in the Finder. But if you remove an application from Launchpad, it’s gone from your Applications folder, too; it doesn’t even show up in the Trash. However, you can download it again from the Mac App Store with (in many cases) your data intact.

The Dock

With a few exceptions, the Dock in Lion is pretty much the same one you’ve known for years.

The biggest change is subtle: the little blue dots under icons that indicate which programs are running are (by default) gone, but you can turn them back on in System Preferences.

Another change is subtler still: if you’ve activated the Application Exposé feature (in the Trackpad system preference), you can swipe three (or four) fingers over an application’s icon to show the windows associated with that application. In applications that work with documents, you also get a Cover Flow-like list of files that you’ve worked with; clicking any of them will open the document.

One last tweak: applications from the Mac App Store no longer jump into the Dock; they go to Launchpad instead.

Finder

With Mission Control and Launchpad, it might seem like Apple is shifting the focus from files and folders to applications. But Lion’s Finder has a few welcome improvements.

One of the most significant is a new All My Files section in the sidebar. Select it and you’ll see all the files available for you to work with – documents, PDFs, images, music, movies, and so on.

There are also some new view options. You can opt to organise files in any Finder window by Name, Kind, Application, Date Last Opened, Date Added, Date Modified, Date Created, Size, or Label. Files are then grouped in sections; choose Date Last Opened, and files are sorted into sections for Today, Yesterday, Previous 7 Days, and so on.

Spotlight

Spotlight has a few clever new tricks. You can search Wikipedia and the web from the bottom of the Spotlight menu. You can also drag search results from the Spotlight menu to an email message, a folder, or AirDrop – Lion’s new local file-sharing feature. And you can now use Quick Look on almost anything from the Spotlight search bar: hover your mouse over an item, and a fully scrollable preview will pop up to the left.

Gestures

Apple has supported gesture-based input for a while. Lion takes that support to a whole new level. To take full advantage of gestures in Lion, you’ll need a multi-touch Trackpad; many of them won’t work with the Magic Mouse or the trackpads on older MacBooks.

Revisions and additions

Some of Lion’s gestures – a more configurable secondary click and two-finger navigation – are revisions of those in Snow Leopard. Others, such as the swipes to switch between full-screen applications or to invoke Mission Control or Launchpad, are new.

Two-finger scrolling works differently in Lion, too. By default, pages now scroll in the same direction as your fingers. That’s how scrolling works on the iPhone or iPad, but it’s the opposite of how it’s been done on Macs. If you hate the change, you can disable it in the Trackpad preference pane.

Also potentially frustrating is the way that Apple has remapped some gestures. A four-finger up-swipe previously exposed the desktop; now you pinch together four fingers. Full-screen Just as Lion’s multi-touch gestures are clearly influenced by iOS, so too is its support for full-screen applications. When you run an app on the iPhone or iPad, it takes over the entirety of the device’s screen. Now, if you want them to, your Mac applications (at least some of them) can do the same thing.

Entering and exiting

To enter full-screen mode, you click on a small diagonal-arrow icon at the upper-right corner of the application window’s title bar. When you do that, the program expands to fill the screen and the Dock and menu bar disappear. If you move your mouse to where those items were, they’ll temporarily reappear.

Once you’re in full-screen mode, you can navigate to other full-screen applications – or virtual desktops – by gesturing (swiping sideways with three or four fingers) or by pressing the left or right arrow keys while holding down Control. You exit full-screen mode either by pressing Escape or by moving your mouse to the upper-right corner of the screen and clicking on the full-screen toggle.