I upgraded my Vista SP1 Home Premium to Windows 7 RC1 with no problems. I downloaded Win7 and burned the iso on a DVD. Used a USB DVD player to launch the setup program. Initially it failed because of McAfee and need for more disk space. It said it needed 13G of space to perform the upgrade. I uninstalled McAfee and several applications. I also reduced the size of the pagefile and turned off hibernation.
It took forever to do the upgrade, 2-3 hours. After the upgrade everything worked fine, drivers, applications, etc. Even the Verizon VZAccess Manager. I reinstalled the applications and everything is fine. I went to the McAfee site and did a search on Windows 7 and found their beta program for windows 7 users. I was able to download the beta and install on Win 7.
Sleep, close lid sleep, and hibernation are all working ok. I didn't have to install any drivers as it must have used the existing Windows Vista drivers or brought it's own with it.
My configuration: 1G RAM, 32G SSD
, no webcam.