The walkthrough is broken into two segments, one for the Autobot campaign and another for the Decepticon campaign with 6 plus hours of footage, across 45 videos of around 11 minutes each. One of YouTube's best features is its playlist so can check it out after the break or use the links to look at the individual videos to "like" the videos and comment (to bad YouTube doesn't allow the same for playlists).
A final note, High Moon Studios is offering double experience points this weekend for anyone playing the multiplayer matches online via PC, 360 or PS3. The Double XP starts at 9:00PM and ends whenever they feel like it (but probably after the 4th).
The last video of Decepticon campaign (Chapter V) currently isn't part of the playlist, so you can find it here.