I've been using one with a porter cable 690 for many years. Mine is actually a pre-release version I received for testing. It's an excellent speed control for anyone using a router.
However, they aren't cheap, at about $175 delivered. Imo, a better option is to go to a 2.2kw chinese spindle and VFD, which you can get for about $325, provided you have 240V available.
But if you want to stick with the Porter Cable, yes, the Super Pid is a great upgrade.
Gerry - http://www.thecncwoodworker.com