I like it a lot, although my early enthusiasm has been tempered. First, there are only two companions (aside from generic hirelings) in the game. there's talk that Larian will be adding a number of fleshed-out companions in an August patch, but I'm enjoying the game too much to put off playing it to wait.
Second, there are not a whole lot of different enemy types, at least in the early game. It's not as bad as, say, Dragon Age 2, but it's noticeable.
Other than that, I find that the game is great fun and a welcome throwback to old-school RPG design. I thought I would not like controlling both main characters' dialogue options, but it's actually very cool. Rather than shape a single Shepard or Hawke-type protagonist, you get to define two protagonists and their relationship to each other. Mine are opposed on a number of issues, which makes one of the companions quite critical of the protagonists.
The lack of quest markers or obvious quest paths takes a bit to get used to, but I've adjusted just fine after a few hours of play.