Honestly? This seems perfectly good. A 4/5 at least, I'd say.
Harley isn't exactly like in the comics, but I'm okay with movies doing their own thing as long as said thing is a good one. And honestly, on the whole she's pretty darn faithful, and keeps her sense of fun.
Deadshot is cool. I haven't read a lot of comics about him, but judged on his own merits Will Smith seems good as usual.
The Joker? Weeeeell, I know the tattoos are controversial--or rather, not controversial, because everyone agrees that they're a bad decision and npbpdy's arguing about it--but I honestly think that they might work with this version of the Joker. And while I'm not crazy about what I've seen of him, I don't have enough to go on.
Like rosac said, Killer Croc shoulda been bigger but is good apart from that.
Amanda Waller isn't quite big enough, but still basically good and not the New 52 lbs. version.
All in all, I think the movie as a whole looks fantastic.