Transformers original run time: 143 minutes.
Transformers: Serious Edition run time: 104 minutes.

In case you have not realised around 39 minutes has been cut from the film. Here is a full list of what has been removed:

*Removed entire opening so first Autobot immideately after credits. This means getting rid of the troops talking in the plane while they land, but it saves around 3 minutes of time.
*Cut down garage scene to make it less comedic, as it's pretty much bad joke after bad joke.
*Removed Sam meeting Megan Fox for the first time. It just adds character development and doesn't really get the story moving along. Yes, no hood scene. :(
*Removed short lines throughout the film to prevent repetition.
*Cut police station scene. Continuity slightly suffers but too stupid to keep.
*Cut most of the dessert action scene up to where they call the Pentagon, to keep a faster pace and to save a bit of time again.
*Cut scene where the Australian woman meets the black hacker, again too comic.
*Small cuts made throughout to remove humor and make it have a shorter lengh.
*Removed scene where secretary finds out about Sector 7. A bit stupid that this whole time he didn't know about this.
*Trimmed down scene where Autobots talk about humanity: Now all they say is the location of the AllSpark.
*Trimmed down scene where Sector 7 agent tries to make ammends with Sam. No more "You hungry?" crap.
*Edited Megatron scene accordingly so that the Secretary doesn't say "How come I wasn't told this whole time?".
*Slightly rearranged the discussion of the Cube/AllSpark so that it is all explained in one continuous scene instead of being split up by that annoying little robot.
*Got rid of the annoying little robots' scenes in Hoover Dam. Because he is annoying and also for a little change later on.
*Made it so that you don't see the Decepticons getting ready to attack Hoover Dam: Simply after demonstrating the power of the Cube the room shakes before the Secretary says they have found the location of the Cube.
*Rearranged around 4 scenes so that the Autobots driving to the city and the Secretary of Defence calling for backup from the marines is all one continuous scene instead of split up.
*Deleted Bumblebee being taken along in the car, a bit too over-the-top. Instead in the middle of a fight with the tank Decepticon with the Marines suddenly he gets shot in the chest by Bunblebee, it shows him as a bit more of a heroic figure.
*Clipped bits of dialogue that were redundant and didn't push the story along.