You can only use the SoundToys Pure Pitch plug-in on TDM (HD) systems. For this reason I've only used it on the systems we have at the studio where I work, which are all Pro Tools HD systems. The main system we have runs this on a MacPro desktop computer that has 10 GB of RAM and dual 2.66 Ghz Intel Xeon processors. I've never experienced any issues with this plug-in and no one running it should be either...
I'm an overall big fan of the SoundToys Pure Pitch plug-in for a number of reasons. My first and main reason beyond the effectiveness of the sound, is the interface, as it has a very user friendly make up and couldn't be much easier to use. At the same time, there's a ton of features and parameters to play with, so the possibilities are wide. There are a lot of plug-ins out there like this, but as far as strict pitch shifting plug-ins go (not tuning), this is probably my favorite due to the collection of parameters and smooth sound. Obviously, only those with TDM systems will have access to this, but even if you do have access to a system that has it like me, it's worth using there and printing tracks. Pure Pitch is a great professional pitch shifting plug-in to have in any HD system!