They're OK. They can be unpredictable, and like others here have said, if you mess up on some of them, you'll really eat it in the end. I've beaten some up and they didn't care. Others turned out so tiny or stunted and I couldn't figure out why, even if I never messed with em. I've had a few that just refused to flower and sat in my space eating and growing. It's kind of a crap shoot, or at least, my last few attempts with autos felt that way.
That said I'm on my third auto from Mephisto, and very impressed.
I plan on picking up some gear later this month, but I think I'm gonna let my stock of auto seeds run out (the Mephistos are the last).