There are lots of issues that have to do with technical limitations or problems, either with the phone or various apps; however, there is one rather large issue that has to do with a policy decision made by Verizon, rather then being based upon a technical limitation. According to reports elsewhere in this forum, Verizon made the call to not allow simultaneous phone and network access and that does put a serious artificial limitation on the user. If you have an instrument that is capable of multi-tasking, but you articially limit the use of that capability, that's a shame.
The folks at Apple and AT&T are having a heyday with that restriction right now, mainly because they have very little else to harp on. That is an issue that AT&T is right to rag on Verizon about, but one that can be easily resolved by Verizon.
It seems to me that Verizon is taking a "get your toes wet first" appraoch to this whole thing. They are trying to avoid the mess that AT&T finds themselves in right now, where the hundreds of thousands of iPhone users have reportedly swamped their 3G network by using streaming video apps. I can't blame Verizon for trying to protect their network by going slow and better understanding the types of demand that these phones can put on the net; however, there are ways of doing that without artificially crippling the phone itself. and by extension it's users.
Almost all of the carriers will eventually have to have policies that either retrict what can be done on these handsets or set up useage-based billing structures for charging users of excessive bandwidth. In these early, formative days of the adaption of smart phones, however; Verizon and all the other carriers need to be more supportive of users who are trying to see what reasonable and helpful things can be done on them. I hope that they quickly see the light on the issue of allowing simultaneous voice and data use for these phones.