It's a good time. It's brisk, has a lot of humor, and it's cool to see. I didn't really understand how a giant magnet in one's chest would "stop shrapnel" but.... who cares! It's Robert Downey Jr.! He glows! He flies! He's got flight attendants who pole dance! He argues with robots! The bad guy (Jeff Bridges in one of the best - i.e. LEAST Jeff -Bridges-like roles I'v ever seen him in) dosn't just steal Tony Stark's business, steal his ideas, steal his technology, and try to kill him, the bad bad Obidiah Stane also uses really really dirty fuel systems and hurts the environment!
So.... see it. It's a fun 126 minutes you won't mind paying $9 for!