It's the best in the series so far, but I don't really see an improvement in visual effects over its predecessor. I'm guessing that's because the first movie in the series set a ridiculously high bar. In keeping to tradition, the movie is also noisy and has overly-frantic action (WTF's going on), and has way too much of it. It also has a shallow story-line and none of the characters are very interesting. Luckily, there is no Tyrese Gibson and Josh Duhamel to help spoil things. There is also no mention of why these primary human characters were so drastically changed... sad.
The movie is entertaining throughout, despite running for over 150 minutes. The evil Transformers were scarily-violent, as they always were in this series. The scariest of them, Megatron, was pretty much cast aside in this movie.