I saw Marvel's latest entry in their shared MCU, Guardians of the Galaxy, today, with my wife and daughter. We saw it in 3D (not IMAX) mostly because of scheduling; I generally eschew 3D if I can. Short version: this is another solid entry in the MCU, and should make a whole pile of money for Marvel. We enjoyed it thoroughly. Was it the best ever Marvel movie? Not quite. Spoilers are kept to an absolute minimum; if you saw the trailers, there's nothing new here for you (although they are somewhat misleading; there are pieces of dialogue in the trailers that definitely aren't in the movie).
Obligatory sfx note: the effects were flawless. Groot and Rocket especially, being CGI characters, were a wonder to behold. Not only were they technically flawless, but they were impressively physically emotive. There's a scene with Rocket in particular that really took my breath away with the pathos that they were able to put into a CGI character. It's a quantum leap beyond Gollum (and forget about CGI Yoda from Phantom Menace).
The rest of the cast is very well done, although Zoe Saldana as Nebula seemed a little flat to me. Chris Pratt as Henry Quill/Starlord steals the show, although Dave Bautista's Drax the Destroyer was a close second, with a lot of unexpectedly great lines and a real arc that let him change from the person we see at the beginning of the film to his final character. His was the character who most grew from their experiences.
Good villains make great movies, and Ronan the Accuser was a good villain. He actually had a real motive, which was wonderful to see.
There are some tie-ins with the rest of the MCU, specifically stuff we've already seen in Avengers and Thor 2 (which again shouldn't be a big surprise to anyone), and it should surprise no one that a GotG 2 is already in the planning stages. But what interests me more, as a fan of the whole ginormous enterprise that Marvel is attempting to create, is where Guardians fits into the grand scheme. There are at least three different sub-universes within the MCU; the Avengers, the Cosmic, and the Mystic. This film is of course the first real foray into the Cosmic (Thor and Thor 2 were only peripherally so, as the Asgardian worlds seem rather self-contained compared to the rest of the galaxy), and it most definitely links the Cosmic to the Avengers universes.
A lot of people early on said what a big risk this film was, and that may be true, given that it was based on a fairly obscure team of heroes in a new setting. But I see it more as testing the waters for other similar efforts, namely, the Cosmic universe. I think the inevitably positive response (and huge box office) of Guardians means that Doctor Strange will be seen as less of a risk in itself. It all weaves together.
Getting back to this film specifically, there is a lot of humor in it, but it's not nearly the goofy space-comedy that I was expecting. There's a lot of wisecracking from nearly everyone, but it's nothing more than one might expect from a particularly energized episode of Buffy the Vampire Slayer. There are one or two truly bizarre moments, which will absolutely baffle those who aren't familiar with the comics (not just GotG, either; there's a bit of fan-service in there that is just out of left field, but all the more wonderful for it).
The action sequences were well done, but perhaps a bit pat. I found myself enjoying the repartee between the characters during the action than the action itself, which might not be entirely accidental. That sort of banter is where the relationships between the characters lives, and that is most definitely the heart of the film, just like it was in Avengers.
This is a terrific Marvel film. It's not my favorite Marvel film, though; Avengers, Captain America: The Winter Soldier, and the first Iron Man definitely top it in my personal list of favorites, but it is a completely solid contender against stiff competition. Absolutely worth seeing in the theater, and it should have a lot of rewatch value on television, too. Don't bother with the 3D if you can avoid it, though; it didn't add much, and was as annoying as it always is when there was a lot of contrast between bright white and dark areas. Lots of double-images in those cases.