Right now I'm running the Digidesign AIR Talkbox on a Mac Book Pro lap top 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 most of the time. While I've run Pro Tools 8 on an HD system as well, the AIR Talkbox plug-in isn't one of the AIR plug-ins that I've run on an HD system. I've only had a need to be running one instance of the AIR Talkbox plug-in at a time in Pro Tools - really just to see what it was all about. I haven't yet had a need to run more of them than this, so I can't really speak to how well it would perform under harder conditions...
Beyond having Vocoder plug-ins available in my suite, I don't really have too many talkbox plug-ins, so I was happy to gain the Digidesign AIR Talkbox when I got Pro Tools 8. I'm happy that I upgraded as I got a whole bunch of free plug-ins that sound good and are very useful. While generally not the most practical plug-in to use on a daily basis, I can definitely see it coming in handy now and again if someone is you're looking for a talkbox like effect. There is an extravagant amount of versatility here, but the sound quality is more than adequate and there is definitely a good amount that you can do with it. If you have Pro Tools 8 definitely check out the AIR Talkbox and the other AIR plug-ins available in the suite!