I've made it into the Autobots portion of campaign mode, and I'm still enjoying the campaign gameplay so far.
In terms of game dynamics, I find the weakest part of the game might be the special attacks, at least on the PC version. Half the time I forget I have them; the other half of the time my pinky can't reach the right key to use the one I want (and I don't seem to be able to adjust the keyboard layout).
Really, this seems to get to the heart of the biggest drawback of the multiplayer modes as well -- a lack of control and customization. Not only is the lack of chat on the PC a major weakness, you can't even choose what server to join...and it doesn't look like anyone can set up their own self-designed matches. It would be nice if High Moon could loosen the leash on PC players.
In terms of the narrative, the game is doing a great job of creating its own history and mythos. I might not agree with every choice (Why would you assign an unreliable sky commander to guard duty for the most powerful resource on your planet? Why would Optimus be called Optimus before he became a Prime?), but those are mostly quibbles. My only major complaint on the storytelling side so far is that I'm not sure I always buy the voice casting. The actors themselves are doing just fine...but I'm not sure the voices always fit the character.
All that being said, this is pretty much the Transformers game that fans have always fantasized, so kudos to High Moon for pulling this off where so many others have failed miserably and painfully. I'd say this is one of the only recent games I've played that lived up to its seemingly ubiquitous hype.