Opening scene is around 10,000BC - pyramids aren't built at this point (optimus' voiceover says transformers have visited earth before he thought they originally did), the primes are building the sun harvesters, the fallen goes AWOL and starts killing humans. It then jumps to present day - so nothing more is explained
The next time you see the fallen is on cybertron (or the nemesis as some believe)
Jolt has little screen time, aids Ratchet in the Jetprime combination.
Sideways shoots one particular bike to death/badly injured. No combination for Arcee bots. Sideswipe is shown transforming from vehicle to robot mode at a distance, happens right before the skidding scene. Kills Sideways off in first scene, very cool.
Prime shoots Demolishor's head off. Has a few lines something like "Do you have any last words?". Then Demolishor mentions of the Fallen(yes he talks through a decapitated head), Optimus then blows the head to bits.
Soundwave is massive! Ravage ejection scene gives a picture of his scale. Never transforms and has this epic scene where he wraps around some satellite. Talks through his head, G1 style monotone voice, darker more demonic feel, same emotionless touch! Ravage is awesome, spits out tiny bots that combine into some skeletal form to steal the Allspark shard. Ravage destroys the base from outside while the bot escapes from within, super epic.
Alice the pretender is killed. Forest fight is simply phenomenal. Starscream gets his hand chopped off, Grindor is killed. Prime has this awesome line, "I'll take you all on!". Gets stabbed in the back by Megatron. Prime in stasis lock is brought back to base by NEST and the Decepticons are chased away by Autobots who arrive in time.
Megatron and Starscream holding his broken hand fly to the city, Megatron slaps SS for his failure, G1 style with SS bowing his head down half the time. The Fallen refers Megatron as an apprentice. Darth Vader-Emperor relationship. Mixmaster is seen on the bridge to broadcast Fallen's message. Sam's parents in paris are then kidnapped by Rampage, the only named Constructicon.
Bumblebee rips off Rampage's head and kills Ravage. Final battle sees the Fallen arriving, has telekinetic powers. Devastator is formed from at least 7 Constructicons, they have NO individual robot modes and are completely different beings from their "robot mode" counterparts. This makes the Combiner giftset accurate. Devastator has huge balls, Simmons calls them "The Scrotum" *no kidding*. Massive scale, can expand vortex at will. Bonecrusher is seen. Scorponok appears and injures Jetfire badly, to the extent where Jetfire's parts start falling apart. Touching scene where Jetfire rips his own spark off, saying it was an honour to see a Prime survive. Jetprime combination happens, bad ass. Can adjust thrusters forward to form blasters. Flies around attacking Fallen and Megatron on pyramid, other Autobots just stare since they can't fly up. Starscream escapes when Megatron and Fallen start having a hard time, saying "Sometimes its the coward who survives". Fallen is killed, Megs flies away with half his face burnt off.
Movie ends ALA movie 1 style, New Divide plays at the end of some wise words from Prime.

Ransack is seen in a photograph, not featured in movie.
Mark Ryan(Bumblebee) voices Jetfire!

In the battle that takes place after the combination, there are shots where Prime is damaged resulting in Jetfire armor parts dropping off. At the end he completely loses it.