Yeah, I thought season 1 was a bit meh, nothing special about it though it enabled you to really discover who the characters were and actually start caring about them. Had some real big laughs with season 2, and we've started watching season 3 and are enjoying it just as much.
The Dave character is a bit bland, and they did well to completely dumb Elisha Cuthbert's character. Overall the cast is very good, you really actually care about Max and Penny (very likeable characters) and the chemistry between Brad and Jane is incredible, very very believable. It's also very funny cos my girlfriend is a control freak just like Jane and I recognize her traits in quite a few of the situations. Damon Wayans Jr. acts too much if you know what I mean, you can tell too clearly that he's acting, but it actually works perfectly for this kind of sitcom and he's maybe my favourite character. His delivery and timing is great.
Overall, just like most sitcoms, it's a lot of re-hash of what's already been done and you could say that Friends inspired it more than a lot, though 1) it was very funny how they addressed that point in season 2 and 2) even though I love Friends and have seen them all many times, it's not to a point where I feel it's plain copying, and it hasn't stopped me enjoying it at all (which is a feeling I had a few times when watching HIMYM, even when it was still good).
So yeah, I'm enjoying it quite a bit (and my girlfriend is really loving it, watched both seasons in about a week, so thanks for the tip!
