I played in a three-man game as part of teaching someone new how to play, and I was pretty unimpressed. The new player got out a Drow Priestess with Lolth's Blessing, so he was drawing the same number of cards as both of us put together. It would have made sense for us to gang up on him at this point, but then he would clearly have been beaten up - even with the same number of cards, he isn't doing the same amount of damage - and that wouldn't have been a good introduction to the game.
My impression is that two of the three players can choose to make the game into a two-person game by focusing on one player. Does anyone have any house rules for a three-person game that help prevent this scenario?