Vista to Win7 upgrade = crashing with an uptime under 2 min.
Clean Win7 install = running OK
Detected all of the hardware in my fairly-new Dell laptop except the Video card immediately - the video card (Quadro NVS130M) initially was missed but got picked up on my first actual reboot - I'm not sure if Windows update was involved or not.
Don't like some of the UI changes or the new taskbar/notification area, but otherwise it's not bad. Since I couldn't get the upgrade to go (and lost a bunch of time to a restore from backup), it's on a spare HD and I have not had much time to play with it.