Too many characters, too many disparate story strands - some of which just disappear into the ether (presumably to be resolved in other Marvel movies) - and an inevitable lack of focus all risk to pull it apart at any moment.
Regardless... it's a gargantuan feat of film-making - just to have successfully created something remotely edible out of such a rich stew of ingredients. It's the cinematic equivalent of Ready, Steady, Cook - Joss Whedon got handed a lemon, a jar of anchovies, and a radish, and somehow made a passable beef stew out of them.
But anyway. If nothing else, coming in the same week as that dreary Batman Vs Superman trailer, it proves that Marvel has cinematic super-hero adventures sewn up. Weird then, that when it comes to video games it's DC Comics that has the upper hand. Click through for video evidence of this thing we just mentioned.