When I describe myself as an old-school Avengers fan, that isn't to say I've been one for some great length of time (unless six years seems like a lot to you), but instead to suggest that I'm primarily a fan of the old-school (i.e. pre- Brian Michael Bendis) Avengers.
Perhaps a bit of an explanation is in order. To make a relatively long-ish story short(er): My undergraduate thesis was a 36-page mock series bible for a hypothetical Marvel comic book series. I'd recently picked-up about half of the first Secret Wars from a nearby flea market - and I found myself fast becoming fascinated by Kang the Conqueror. I mean, what was this guy like when he wasn't relegated to the shadows of Victor von Doom?
I bought the Kang: Time and Time Again trade-paperback to find out - and I discovered that the eponymous Conqueror is primarily known as an Avengers villain. This led to my purchasing the Council of Cross-Time Kangs storyline from issues 291 to 297 of said team's series - and while I'd eventually go on to use him in my aforementioned academic proposal, I was no longer satisfied with just reading about Kang alone.
No, I was now actively tracking down anything Avengers-related - my wont for ascribing the modifier "old-school" to myself (due to Disassembled having rendered far too many of my beloved characters either functionally irrelevant, or literally deceased) notwithstanding! So what's my opinion of this movie, given that I'm sufficiently familiar with the source material?
In a word: It's awesome.
Seriously - this does a lot to redress my misgivings after the generally lackluster Iron Man 2! Sure, it isn't absolute perfection - Brain Blessed's absence alone is criminal (I would've even accepted John Rhys-Davies as Volstagg, instead of whoever it was that we actually got!) - but it's still by far the best cinematic outing we've seen from a Marvel character since Robert Downey, Jr.'s initial foray into the genre!
What more could you possibly ask for? How about an unexpected big-screen debut from a character who's going to figure more prominently into future films - and the now-obligatory bonus scene after the end credits as well!