I installed W7 on my Sager which is my older machine. I installed the Beta version. I got a message that my wireless card may not work with Win 7 which is the Intel 2915 ABG card and my Realtek sound driver. I connected by wire and the Windows Update installed every thing i needed beside the 2 about. I downloaded the realtek drivers and installed and I had sound. The Intel drivers were a bit more tricky. I downloaded the driver and executed the setup.exe and it didn't install. But after seeing on a Win 7 forum I went to device manager and selected to find driver whe it searched my computer and found the same file I tried to execute it installed successfully. I have installed Win 7 RC on my Acer 9810 as a virtual desktop using MS Virtual PC 2007. The biggest difference with virtual desktop and installing as the only OS is drivers. The virtual system uses generic graphics drivers and won't reach the full resolution with Vista. Also their was no sound. I didn't try to install the drivers within the virtual system. I was able to use my wireless card but after some tweaking.
One thing I haven't used but have seen demonstrated is using XP mode in Windows 7. it is actually pretty neat. What you do is bring up your XP session in microsoft virtual pc and install that application. After that you never have to start your virtual session to run the XP app you installed. It creates a shortcut on your Windows 7 screen and when you click on it the virtual session runs transparent to you the user which is really neat.