This film is a thoroughly enjoyable, hilarious 2D comedy. I think it works very well in 2D and although it has violence in, it is a comedy about an independent army unit and if it had been in 3D I feel the film would have been more focused on special effects than the humour. Also one of their 'plans' wouldn't have been as funny or as effective if it was in 3D.
It is based on the famous TV series but with a fresh cast and new missions. Whereas the TV series was about the team's missions, the film is set long before that and tells a very different story. it is made even better because it has a fairly low rating (12a) so it has a wide audience.
I think you will enjoy this if you are a fan of the old A-team or a new viewer. And although it is based on a plot with adults, I feel that teenagers will enjoy it a lot too.