I can tell you first hand that I am using Adobe CS4 Extended on Windows 7 Ultimate 64 bit and have no issues. Keep in mind that I have a powerful system and use more than one CPU along with 10GB of RAM. If you plan on doing anything intensive I would strongly suggest at least 8GB RAM or more and consider a workstation type of motherboard that supports duel-CPUs. Also, you will need Windows 7 Pro or Ultimate to take advantage of more than one CPU and more than 16GB of RAM. All I can say is it really does make a BIG difference and a lot of crashes or issues (not all) can be solved with better hardware and more memory.

Jeff

Development on: Mac Pro 2008, Duel-Boot OS - Snow Leopard 10.6.6 & Windows 7 Ultimate 64bit, 2 x 2.8 GHz Quad-Core Intel Xeon , 10GB 800 MHz DDR2 RAM, NVIDIA GeForce 8800GT.