It was great. The Knightmare scene and Justice League cameos (except Wonder Woman) should've been cut out, but overall it was fantastic. Definitely better than Age of Ultron, Iron Man 2, and the Thor movies at least.
I'll give it that, it's certainly far more ambitious in scope and theme than almost anything in the MCU. I respect what DC is trying to do a lot more than what Marvel is doing, which has a fundamental shallowness to it.
The problem is, they're failing at it, and one of the main reasons is that their writers just don't get what these characters are supposed to be. Batman was not Batman, Luthor was not Luthor, Superman was barely Superman, and Wonder Woman was just a glimpse of what she should be (I'll reserve my judgment until her own movie comes out, though). It's a terrible, terrible missed opportunity, and it's all the more frustrating because I'm a DC fan and I'm rooting for them against Marvel. Well, I'll concede that they didn't develop Superman very much, but Batman was Frank Miller's Batman (now whether you consider that Batman or not is a different story) and I enjoyed their new and original take on Lex Luthor.
Frankly it didn't even seem that out of sync with the Kevin Conroy Batman from Batman Beyond.