are lines long as with the vatican museums?
No, the lines are not nearly as long. To
save even more time buy your tickets at
Palatine Hill where there are no lines at all
then walk right in the Colossium as you are
waiting at the site not to enter, but rather
to purchase tickets.
We considered this one of the best tips in the Rick Steves book. When we visited in the fall, the line for the colosseum was very long, but there was not one person at the entrance to Palatine Hill. Buying our tickets there was a huge timesaver.
Buying your tixs at the Palatine Hill as Rick recommends is the way to go. More people seem aware of this trick than a few years ago but it is still a huge timesaver.
My wife and I were in Rome last week and the lines were long but the palatine hill ticket line was empty. When you go back to the colloseum stay to the left and walk right through.
Rick's Italy guide also talks about the Archaeologia card that can be used for admission to several sites. You can get them at the TI at the airport as well as at the various venues.
Also look into the RomaPass (www.romapass.it).