Vista runs proe with no problems. If there is any problem with speed I have never seen it. It may show up in benchmarks but then the benchmark is not the real world and how you use the software. It has been a real long time in the computer arena since we had to wait for your feature to regenerate in a reasonable amount of time.
Now on another note - I would skip vista all together and go with Windows 7 64 bit. I have been using it for the past 3 week and do not have any problems what so ever. I am not running any windchill or PDM but everything else is working just fine.
Ron