Transformers fans (pretty much all males my age) were greatly disappointed a year ago when we heard that Michael Bay would be directing this movie. But having just seen it, I was very pleasantly surprised. He didn't shit all over everything, and the adaptation is reasonably on-key for a live-action movie. In fact, the only problem was the classic Michael Bay problem of "the action sequence is three times longer than necessary." Luckily in this film, you're really interested in looking at the Transformers, so the problem is somewhat ameliorated (the final action sequence only feels about twice as long you think it should be).
The characterization of the Transformers is rather shallow ("This is Ironhide, my weapon's expert"), but given that the movie is about the exposition of the Transformers coming to Earth, it actually does a fairly good job of developing the character relationship between Sam Witwicky and Bumblebee, spending a rather un-Michael-Bay-like amount of time doing this. There is even an extended scene where Sam Witwicky returns to his house to look for something while the huge Transformers try to hide from his parents which appears to have been included solely for comic relief (it doesn't advance the action significantly and goes on for quite awhile). There are also a couple of nice "wink and nod" jokes. Shia LaBeouf does a really great job with his role, along with a couple of remarkably high-profile actors (Jon Voight and John Turturro, who is clearly having fun goofing off).
The live-action visual style is good. I read somewhere that the CG team had actually tried to recreate the original blockier style of the cartoons but it ended up "looking retarded," so they had to come up with the new style. Supposedly they actually went to auto shops and learned where all the parts were inside the vehicles, so that significant amounts of the parts that you see moving around correspond to real parts in the cars.
The well-known deal with GM (where all the cars are GM models) turns out not to be irritating at all. Some die-hards may take exception to this, but I feel that the concept's explanation of "they scan things in their environment to get models to transform into" is a sufficient one. It's a bit unrealistic that they would have all happened to GM models (statistically, they would be Honda Accords), but perhaps the field they crash landed in happened to be near a bunch of GM brand dealerships.
So if you were the fan of the original (or you just like a good action movie with machanical things - cars, robots), here's your recommendation - go see it. You won't feel like you wasted your time.