I tried both CreditKarma and TurboTax this year.
Credit Karma missed some things in my NJ state return that would have cost me a couple hundred dollars. There didn't appear to be any way for me to manually include a correction, so I ended up filing with TurboTax (free version).
This wasn't even a particularly esoteric exemption, I expect it would have come up with anyone who worked for two different companies in the same year. Aside from that, I'm a very standard case.
http://www.state.nj.us/treasury/taxation/njit16.shtml