The Digidesign AIR Fuzz-Wah is a free piece plug-in available with Pro Tools 8. You can't get the plug-in anywhere else, as it is solely a plug-in for Pro Tools 8. Once you've gone and installed Pro Tools 8, there is no need to take further action to get this plug-in installed, as it does it automatically when you install Pro Tools, similarity to the older free plug-ins for Pro Tools. As far as the interface goes, it definitely has more going on than the other AIR plug-ins, but it does share the same look and style. The main parameters include drive level and mix level for the drive, as well as for pedal, filter type and mix for the pedal level, and then an overall mix output. The plug-in then has sections for fuzz, pedal min, pedal max, and modulation. Each has their own parameters to play with as well, so as you can probably tell this isn't the simplest plug-in in the AIR free plug-in suite. Having said this, I still don't think that it is a hard one to manipulate, as everything makes pretty good sense once you play around with it for a minute or two. I don't think that they make a manual for this plug-in, but I could be mistaken.
I'm currently running the Digidesign AIR Fuzz-Wah on a Mac Book Pro that has a 2.2 Ghz Intel Core 2 Duo processor and 4 GB of RAM. I run Pro Tools LE 8 with a Digi 002R audio interface or a Digidesign Micro Box if I'm on the go. While I can't say I've ever had a problem in terms of performance with the AIR Fuzz Wah, I should also say that I've never had a need to use more than one instance of it. So while I don't think that users will have a problem running multiple instances of this plug-in if they want to, I can't say so for sure from experience - it really just depends on the system you're running it on.
The Digidesign AIR Fuzz-Wah is definitely one of the most in depth plug-ins in the AIR suite, but I don't think that I'd say it is one of my favorites, or at least one of the most useful for me. It definitely has a clean sound and you can do a good amount with it, but for what I do I haven't found myself using it all that much. I do like how much versatility there is with it, so judging from that I do believe that people will be able to find a lot of uses for this. If you've got Pro Tools 8 you really have no excuse not to at least try it out, and if you don't I'd definitely recommend upgrading!