Cute movie with one HUGE flaw (Spoilers!)
...at least for me.
I think that the two characters who also remembered the Beatles should have been introduced much earlier.
Why? Well, for me, I spent most of the movie waiting for the explanation. Waiting for someone to show up to explain to the audience what was going on - how the alternate reality happened, was Jack in a dream, or was this being done by aliens, angels, etc.
I didn't realize we weren't going to get an explanation until the two characters showed up who told Jack they remembered the Beatles too - apparently the only two people in the world who did.
Once I knew that we weren't going to get an explanation, I was able to relax into the storytelling. But up until that point I was just impatiently waiting for the explanation, and was really irritated when it finally showed up 15 minutes before the end of the movie.
If those characters had shown up earlier, they could have been there to give Jack guidance and sympathy; as it was I don't think they got nearly enough screen time. But oh well.