Drivers - easy answer - if it has a vista driver - it will work. The core kernel is vista based (don't let that scare you off - its much better - just used vista as the foundation). So if you can't get vista drivers for your HW, then it may be a problem for you in 7.
Stability - is great. I haven't had a single problem out of this box yet, and I have TRIED to cause it problems.
Program compatibility - well now there are a couple of things here. If you run 64 bit - no really old 16 bit stuff will work or install. There are ways around it, but if you have to use legacy stuff - avoid the 64 bit version. However, also remember there will be no 16 bit support from now on - so you might as well move away from 16 bit apps if your using them. Also - a couple of programs don't recognize the OS - I have an epson printer that installed great, worked great, and upon reboot is now generic. Tried updating the drivers and the app didn't recognize 7. These issues are short term - but they are there.
I also mentioned daemon tools not working - but clonedrive works great as an image mounter as is noted.
You mentioned DX10 - I have bad news. You won't get DX10 with 7. It has DX11
- though the word is they may swap down to 10.1 when they ship due to nvidia not having the ability to get their cards up to standard.
As for 64 bit - do you want it? Well - do you run over 3 gigs of ram? If so - yes.