Yeah, I really like Source Code too, but that ending doesn't really make any sense to me, and has always sort of bugged me how they didn't address what went down there. I mean, there must have been a lot they didn't show us about how it can't just be that easy to step into some guy's life who must've had a family and a job and bank card codes that Gyllenhaal wouldn't know and a place to live he doesn't know about and an entire identity and established life that he can't possibly just comfortably step into.
Yeah, they kept it to the idealistic happy ending, which is fine and all, but realistically it wouldn't be all roses.
And I had trouble understanding how the idea of using a dead person created time travel, because interacting in the source code went far beyond simply extrapolating information from the dead guy's mind. I also don't know how the scientist could create an alternate timeline like that without realizing what was actually happening and whatever.
But as I said, accepting all of that, I enjoyed how it played out a lot, and thought it was a great movie.