Just realised I had this thing sitting as a draft for ages. Derp.
tl;dr You know if you're going to like it from the moment you read the title. Some great set-pieces and amusing silliness from the people. There are issues, but Transformers accomplishes what it sets out to do very well.
Or, maybe: Transformers: Dark Side of the Moon - A Defence. Not that, really, this should be they type of film that as a snobbish pseudo-intellectual I really should be defending. The Transformers films are essentially embodiements of some of Hollywood's worst trends, glorying in special effects over characters, fast pace over plot and fart joke level humour over substance.
The thing about criticism, however, is that when you criticise a film, you criticise the film. Attacking the storytelling traditions of the genre is not valid criticism exactly - either evaluate the film at how effectively the film handles its material or devote a discussion to the wider genre and be clear that it's no longer just talking about the film.
So yeah: not only is Transformers DSM a movie about big explosions, impossibly big set pieces and a cast of characters who are essentially all comic relief, it's a film that revels in all of these aspects. Whether intentional or not, I found that there was a lot of amusement to be had by the way that Lebouf SHOUTS ALL OF HIS LINES FOR NO GOOD REASON, and in the cartoonish way that everyone seems to act. These are overblown and silly figures, and no more than a way to frame all the explosions. Only during the finale, when suddenly we're meant to care about the characters, does it fall down - at all other times Bay knows that we're not really going to care about these characters and doesn't bother with the pretense of trying to make us care.
The movie certainly has a style of it's own. Bay's directing isn't run of the mill and he has a keen eye for big shots. Unlike many grim and gritty action flicks nowadays, this is a bright and colourful film, even if it is a little bit garish. Bay's style gives these movies a distinct character of their own, although you may spend a decent amount of time wishing the camera would stop bloody moving.
There are some really cool bad guys in here. Lazerbeak, the evil bird decepticon, is a noticeable presence, but the real star of the show is Shockwave. His giant metallic betentacled form is perhaps the most menacing presence in the film, and certainly the one whose presence you'll enjoy the most. All of the decepticons in this movie, however, do seem to share the same voice. That criticism can be extended to the autobots too - you are going to end up thinking of them as "the blue one" and "the red one". Whilst the humans may all have overblown and silly personalities, few of the robots get any sort of characterisation at all.
This might be a consequence of my low expectations, but the plot actually did have a few surprises for me. It's a movie with a few twists, mostly predictable, but it thunders along at a pace fast enough never to leave you time to actually get your brain involved. Towards the end, the movie becomes really big, with Chicago being ripped to shreds by giant warring robots. Impossible set-pieces are a delight to see, and it definitely feels huge. The film's most major mistake, however, is that the real battle which determines the fate of the world is one that happens between two humans rather than two of the titular transformers. It's not as satisfying or exicting a conflict as putting the conflict between the robots as centre stage.
People love to hate these movies, and I've heard more than a few people gleefully condemning these things. It's not a position I have trouble understanding, but for myself I can't help but feel that this film is enormously entertaining when you take it as what it is. It's not embodying the most sophisticated in cinematic tradition, but that's fine: there's as much a place for this as there is for Black Swan or Submarine in my life.