I played around withit a little when I was studying. If your studying for greater than 3 months and/or doing it along with classes than I would say it has some value. If you're just doing it with 2-3 months of prep though (what most people do) its not really worth it (I needed to flag like crazy the 2ish months I used it). That being said, Its an awfully big financial investment if your doing it long term, when their are cheaper/higher yield alternatives. The mcat really isn't a big knowledge test, so passages are probably more effective than a long term retention tool like firecracker.
Though, if I had the money to splurge, I would have been tempted... use the trial and see if you like it.