I recently did a format and clean install on my Xi 3650 going from Windows Home Premium 32bit to Windows Professional 64bit.
I used the Windows Vista x64 Drivers from:
http://uk.ts.fujitsu.com/support/downloads.htmlHybrid Graphics is working for me. However at least 3-4 of the other drivers there won't install or they produced errors that forced me to remove them.
My system stability was perfect under Vista. Now I occasionally get lock-ups, freezing, and the odd error message. Certain 32bit applications rocket my CPU usuage to 100% and bring my system to it's knees. My fresh install of Windows 7 runs about the same speed as my 6 month old Windows Vista installation did.
My biggest gripe is with using an external display. The Fn+F10 hot key for changing display mode no longer works when the laptop is using the Nvidia graphics card. I constantly have to go into display settings to adjust the output mode / change resolutions. Opening and closing the laptop lid resets these settings even though i've configured Windows 7 to ignore open/closing the lid in the power management options. Once, Windows 7 turned off all my displays, forcing me to reset my laptop just to be able to see anything again. (Even unplugging my HDMI cable didn't restore the image on my laptop screen)
If you intend to use 'Windows XP Mode' you require Hardware Virtualization Support on your CPU. My Amilo 3650 xi processor (T5800) doesn't support it. Yours should work, but only if there is the option to enable it in the BIOS which you might want to check.
I have a few other problems, but they're mostly related to the design of Windows 7. I especially don't like the new Windows Media Player, and believe it or not, after about 10 open windows of say, Internet explorer, Windows 7 stacks them in the same way Vista does, and the mouse-over preview feature starts lagging.
All in all, I'm likely to downgrade back to Windows Vista when I get the time. I was caught up in the hype of Windows 7, but my actual personal experience of it has been frustrating. As the old saying goes; if it ain't broke, don't fix it.