I did it and I thought it was okay... It had similar scores for 3 specialties- the 3 I was interested in, so it didn't help me that much. I think it is good to make you think about different factors that you should consider though. I wouldn't expect it to give you a perfect answer to what specialty you should go into. I think it is worth doing if you have access to it.
I think the program is good only for confirming what you already know. It is a decent program but I wouldn't use it as a decision tool, only a reaffirming tool. By the way the program has been discontinued as far as publishing new CDs and gathering info from surveys.