I can't say that I noticed anything too strange about the brightness overall and I even watched it after reading this thread. Overall, the PQ was excellent.
I did notice that some scenes took take place in the late afternoon that were darker overall (such as when they were preparing for the shuttle launch with the sun low on the horizon) but that made sense given the time of day.
In the later chapters there was still plenty of punch to the whites and lights, though the scenes were generally dominated by shadows since everything seemed to take place between buildings with scenes dominated by a ton of grey robots. On my plasma, it all looked great and I noticed no clipping of the whites. Of course, this is subjective since eye was only using my eyes and I didn't do an A/B comparison between the 3D and 2D version, however... although frankly, an A/B comparison is tough since my TV amps up the settings in 3D mode.
This was on my Samsung PN63C8000 using Samsung active OEM 3D glasses.
By the way, why did Michael Bay have to decide to make every single Decepticon totally gray? It's a total mess in that regard since it felt like Han and Luke were shooting at random stormtroopers. In the cartoon (and animated movie), I always knew who was fighting whom and I actually cared!
Great visuals and AQ overall, but definitely lacking in story and characters. I won't spoil anything either, but damn... Optimus sure seemed angry and vengeful. Not quite the way I'd always thought of Optimus.