I'm running the Avid Reel Tape Saturation plug-in within my home recording rig, which consists of a Mac Book Pro and Pro Tools LE 8. The computer has a 2.2 Ghz Intel Core 2 Duo processor and 4 GB of RAM, and I'm running Pro Tools LE with a Digi 002R audio interface. I can't say that I've had any issues related to performance with this plug-in, as this is a pretty powerful LE rig and can run a good amount at once. I wouldn't think that too many users would have a problem running this plug-in, but of course it all depends on your system.
Overall, Avid's Reel Tape Saturation is a nice little plug-in for a number of reasons. Let me start off by saying that I do believe that the only way to get a true 'tape saturation' sound is by actually recording to tape, but when something like that isn't possible and you working in the box, something like the Reel Tape Saturation plug-in will definitely come in handy for you. It's not a replacement for doing your job as an engineer in the tracking or mixing stages, but it can help to add a bit of warmth to your tracks. While this certainly sounds pretty good and there are a good amount of controls available, I'd always recommend using analog/hardware gear for getting this type of sound, but when not possible Avid's Reel Tape Saturation plug-in is one of my favorite to use.