[nitrous9200]

The Omnia has very good (but not great) hardware, paired with decent software out of the box that can be made dramatically better with the 3rd party ROMs. WinMo is super customizable yet still a bit flaky at it's core as I'm sure you know already. Touchscreen keyboard is actually really good IMO. That being said, my next phone will most likely have a physical keyboard and Android unless WM7 turns out to be amazing.
1) Video playback is great with TCPMP phenom 3. Never had a problem with it.
2) TouchWiz is fun yet gimmicky. I can't see how someone could use it every day, especially when all of the content from the widgets combined could be fit onto one screen.
3) Seeing as the only phone I have right now to compare it to is a RAZR, the Omnia is tremendously better. It's only really good at 320x240 because at 640x480 I think it only does 15fps.
4) HTC never made a WQVGA phone as far as I know. Most of the apps don't work well but Manila 2D does. I used it for a while, it looks great and it's really fast. Other stuff like Teeter is the wrong resolution

ps - I use the mouse a lot when web browsing because it feels natural and the Omnia's build of Opera stinks at clicking on links.