So apparently, the three different versions of Salt on the Blu-ray are all pretty different, certainly the endings vary quite a bit. So your enjoyment of the movies is likely to vary greatly depending on which one you watch, which one you see first, and how you feel good movies should end.
The theatrical release is quite open (i.e. easy for a sequel), the director’s cut is similar but more sinister, and the extended edition is pretty much completely different. We watched the Director’s Cut assuming it would just be a little bit longer, and we enjoyed it. I think I like the ending more than the other two options having read up on them, but we’ll never know which one I would have enjoyed more.
So, be careful if you buy / watch the Blu-ray, make sure you know what you’re letting yourself in for with your choice of cut.