I just went yesterday. I thought it was pretty cool. If you're interested in human anatomy at all, I don't think you'll be disappointed. They do a really good job with all the displays. There is a lot to see. All kinds of full-size bodies, cross-sections showing how each system in the body works, individual organs and examples of the major diseases that affect the organs.
In my opinion, it was definitely worth the $20. Also, we went on a Sunday afternoon and were able to get right in with no wait.