The system that I'm running the Waves Ltd. Maserati GTi Guitar Toner on is Pro Tools LE 8 based, which I run with a Digi 002R audio interface. The computer I'm running everything on is a Mac Book Pro consisting of 4 GB of RAM and a 2.2 Ghz Intel Core 2 Duo processor. For me I haven't had any problems running this plug-in, but of course it all depends on the system you're running it on...
While I don't find the Waves Ltd. Maserati GTi Guitar Toner to be one of the most useful in the Tony Maserati Collection, much of this probably has to do with the nature of the plug-in. For mixing guitars I'll usually use individual processors to give me more control, which is the reason I don't find myself using this much. Don't get me wrong, it's definitely got a professional sound overall, and there's a lot that can be done within this single plug-in, but I like having more in depth controls over each of the individual processors. For something like drums or bass, I find the Maserati plug-ins to be more useful since in general there are more guitar tones than bass or drum sounds. Having said this, the Waves Ltd. Maserati GTi Guitar Toner is a high quality plug-in that is absolutely worth exploring if you've got the Maserati or Complete bundles.