I can think of a few features Colorista II has that I don't believe Color Finesse does (though I'm happy to be corrected if I've missed something):
Power masks for secondaries
The Pop slider (local contrast adjustment)
Personally, I absolutely love Colorista II. The controls are very intuitive, the keyer is pretty nice, the output is clean, and the renders are fast. It's a great tool, if you don't mind the workflow challenges of grading in AE.
Jim, if you're serious about color and you're on a Mac, you should think about DaVinci Resolve. It's incredibly powerful and offers a far better workflow for grading than AE does. The free "lite" version should be out soon if you want to kick the tires.
Of course, there's also the Baselight plugin for FCP just around the corner... it's an exciting time to be a colorist.
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Thanks! Will keep a lookout for the Lite version.
Just picked up 'Adobe® After Effects® CS5 Visual Effects and Compositing Studio'. The older forward by Stu Maschwitz is alone worth the cost of the book, where he argues very eloquently about the importance of 'making it look good' vs 'making it look real'.