According to the video, the infamous "Death Grip" can still affect 3G signal strength on the updated CDMA handset. Additionally, a new two-handed landscape grip, cutely dubbed the "Death Hug," will cause a similar attenuation to your WiFi signal. No word on if this is unique to the Verizon iPhone or if it was merely discovered on one.
You may remember the media frenzy when early reports of the iPhone 4's "Death Grip" were released. Apple surely faced a PR nightmare, but in the end consumers agreed that the iPhone 4 (despite its highly publicized, over-dramatized shortcomings) was among the best smartphones on the market.
The vast majority of users discovered they were not affected by the "Death Grip" problem in every day use and those that were simply bought a case (or received a free one from Apple), which largely fixed the issue.
My prediction is that this "problem" will be similar to the last one: a lot of smoke, no fire. Most users (especially those in areas of strong coverage) won't ever notice any sort of signal loss regardless of their grip. Those that do will either get case or just hold it different. Either way, the strengths of the Verizon iPhone 4 will greatly outweigh this minor (yes, minor) flaw.