I thought it was good, I felt entertained throughout. Not as funny as Ghost Protocol but there was enough laughs in there. Renner's character is unfortunately primarily at the CIA HQ with very little to do, but this is Ethan Hunt's show, so I'm okay with that.
The action was good, maybe a little rehashed, but between car/motorcycle chases, underwater scenes, highwire acts and that insane aircraft opening scene I could not have asked for much more.
The story itself is fairly generic - and it's not curing any cancer that's for sure - but that seems to be a recurring thing in the Mission:Impossible movie.
Anyway, definitely worth the price of admission.