I personally like playing against the AI maniacs. You might have to withstand a little more variance in your bankroll if you take a bad beat, but if you play a little tighter and can nail them just once, it's worth it. Some of these guys will go all-in pre-flop three or four times in a row. With a little luck, I've seen them acquire an impressive bankroll(over $100 at the $25 NL PP tables), and usually lose it just as quickly. It can also makes other players play looser out of frustration, which can make for some nice pots if you get a quality hand to play. Of course, sometimes I end up just folding a lot if I'm getting mediocre or worse hands.