3) Give me a real Open Client
If you're a VDI vendor, a Linux-compatible client is an absolute must. Many thin clients run Linux, so we all know that you have developed Linux-compatible clients. Let us download them. VMware's View open client is just this sort of project, but it's hamstrung by the lack of sound and USB redirection. As I understand it, this isn't a technical problem, it's a political/licensing problem. Fix it. Now.
4) Give me better multimedia support
This is hit-or-miss, depending on the client and the virtualization environment, but these days any VDI build must have relatively flawless video playback. If I head over to YouTube on a VDI workstation, it should look, sound, and feel just like a real workstation. It might not seem like a deal breaker, but when you're running a pilot and looking to assuage user fears that by removing their workstation you're condemning them to constant problems, they'll point to sluggish Flash videos and choppy audio right away.
You try telling a marketing person that they don't need to watch online videos and such, especially their own promotional videos they're trying to make viral. They'll take your head off.
5) Help me tie up Microsoft's loose ends
This is somewhat related to the Windows 7 request. There should be an integration utility provided with a VDI package that handles at least some of the deep dark Windows massaging that needs to occur to have a successful VDI implementation. It wouldn't be too much to offer an installation wrapper that prompts an admin for a Windows XP/Vista/7 ISO image, VLK key, and a few other tidbits, and then creates completely ready-to-run images. Let me boot them, install my apps, declare them gold, and go from there.
There are more. These five are a good starting point, however. As it stands now, VDI is a viable proposition but some greasing of the proverbial wheels will help matters dramatically. So let's get cracking, and help IT lower costs yet again.