This movie is not bad
Purely on an entertainment level, I enjoyed it completely. It's not too long or boring, it maintains good pace and suspense and the acting is fine. I don't even find the Irish accents annoying. It isn't the best movie ever either, but it's a damn sight better than the (slightly) higher IMDB-rated Ford movies Crystal Skull (terrible second-half), Sabrina (bad) and Cowboys & Aliens (absolute drivel).
If you are put-off watching it because you don't want to sully you opinions of the two lead stars then don't be! The soundtrack is good too. The worst thing about it for me was that they cast Arthur Dent as the English "villain" who was out to kill Pitt. Surely all he really needed was a nice cup of tea.