With a name like Kick-Ass, any failure to deliver on the name could only be seen as an utter embarrassment, leaving the film open to countless barbs incorporating plays on the title. With that in mind, I've got the following to say.
Fucking Hell this movie was fun.
For starters, the action scenes were kinetic, well-choreographed, and underscored with good humor. The deaths (and there were many) were always awesome and mostly hilarious.
Everything with Hit-Girl (whose introduction is in the red-band trailer below) was golden. Nicolas Cage* was pitch-perfect as her father Damon "Big Daddy" Macready. Their adorable if not a bit deranged father/daughter relationship worked exceptionally well. Their joking relationship is sweet but superbly counter-balanced with their righteous ass-kicking.
*By the way, this marks the sixth straight live-action Nic Cage movie that I've seen in the theater. He catches a lot of flak from a lot of short-sighted people, but I really feel like this point needs to be made again: Cage is the shit. He does whatever he movies he wants--always giving his all--but he chooses his films because he wants to make them, not because they'll somehow further his career. He secured the rights to The Wicker Man to get that film made because he wanted to remake it. Go back and watch the original. Holy fuck is that a weird, orgy-soaked film. Bravo, Cage. Bravo. This all has meant that Nic Cage has spent the past few years making movies that appeal to him, which in this case do not necessarily equate to films that the typical Oscar-winning actor appears in. And this has been a surprising boon to the moviegoer.
As for Kick-Ass himself, Aaron Johnson channels the everyman--er, everyboy--well, seemingly embodying the younger self of David Eigenberg (Steve Brady from "Sex and the City"). This would seem to be a conscious decision as he is actually quite British as is evidenced by this interview:
Johnson's turn as Dave Lizewski is an endearing one and would tend to point towards a bright future. His friends Todd and Marty (played by Evan Peters and Michael Cera's best friend, Clark Duke) are the complimentary pieces necessary to provide comic relief vital to this film's success.
Across the board, Vaughn & Co. have crafted a laugh-out-loud action-comedy with a healthy love for the superhero genre but a self-aware wit with as good a heart as is possible in a movie that makes you laugh at people getting killed by a little girl. The film never drags, and there really isn't a weak link in the cast or the narrative.
Most importantly, Kick-Ass lives up to its name.