We didn't notice any performance increase directly. But there are no regrets.
Going from 32 to 64 requires a clean install; you can't upgrade.
As a result, we went from a tired, buggy version of Vista, to a snappy, clean version of Win7. Again, any "performance boost" was primarily due to the clean install (that, and I found Vista was never decent OS to begin with).
Another added bonus was that our computers were finally using all 4Gb ram, and many were given another 4Gb for about $40. That sped things up quite a bit, depending how many programs you have running (I have a bunch open all the time), and that in turn removes some wear and tear on the HD as it no longer needs to run as much.
If you really want NX to run smoothly, invest in a pro graphics card such as an Nvidia Quadro 4000.