I've used it and found it a pretty good at what is does compared with other methods of extraction. It's much, much better than the using the Extract Filter in Photoshop and quicker than the Pen Tool on detailed areas and wispy stuff like hair.
I've read on other forums about people having problems with using it, but there's now a dedicated user support group you can go to and ask questions and hopefully get answers if you're stuck on anything.
