Has anyone successfully installed Windows 7 on this thing? Toshiba apparently doesn't support it, and I'm having trouble finding a working display driver.
For ATI Mobility graphics card drivers, use the ATI MobilityModder tool to mod the latest Catalyst drivers to use it with Win 7.
Many have reported success with this method - give it a whirl.
This is the link to the ATI support site for the Mobility X600 that is in your notebook: http://support.amd.com/us/kbarticles/Pages/737-28041SupportforATIMobility.aspx
This basically says that the cards are customized for the manufacturer of the notebook and ATI will not provide general drivers, so if Toshiba doesn't, you're out of luck.
Part of why they don't provide drivers is that the X600 doesn't support all of the features necessary to use the Aero interface, meaning you don't get transparent windows, the snap effects, peek and all of the other graphical goodies. Even if you can find drivers, your experience will be crippled.