I'd rank this as a peer with Under The Red Hood, Crisis on Two Earths, and Superman vs the Elite. It has a clear goal, strong direction and voice acting, and a whole lot of fun, and often twisted, character moments. Deadshot was great in design, depiction, and voice acting ("Mate, you just out-crazied the Joker.") While I am a little confused on why they recast Harley, she was pretty much pitch perfect as well, contributing several laughs and crazy non-sequiturs. Frost was cool (sorry) and true to character. Black Spider was a nice change of pace from the rest of his group, and King Shark feels like he walked out of Secret Six.
And the actual Batman connection was a pretty strong theme underneath it all. Both Joker and Batman are treated as major nightmares for most of the team, and make the most of their screen time. There's a lot to be said for having these two clearly on a level above the team itself, but that just makes the Squad the underdogs, and it works well. Add in C.C. H. Pounder's Wall, and you've got the three forces of nature the Squad has to weather to survive the night.
It's like Quentin Tarantino and Robert Rodriguez made a DC movie.
