Did the ending

It did a little for me. The whole idea behind the movie was to get Joe back into a body, so he could go on and live the rest of his life that he had been cheated out of. When he was stuck into Tom's body and had his memory wiped, he ceased to be Joe. He went on to live Tom's life. I mean, what if Tom was a complete jackass that no one liked? What if Tom had a string of women in his life that he treated like dirt and had that reputation?

Joe got screwed when he was taken out of his body at the moment of the crash and he was screwed again when he was put into Tom's body.

No. The ending made this film memorably melancholy. It was sad to see Joe lose his identity and his special bond with Max, but that very sadness helped make this movie special. The music resonated perfectly with this vibe, by the way. There was a certain kind of melancholy that pervaded Hollywood films based in California in the late 70s, probably part of the long lasting reverberations of a 60s comedown. Other highly commercial films from the late 70s with this kind of sad, California vibe that come to mind are Oh God and The Big Fix.

just re-watched this movie for the 6th time for me, first time for my 12 year old son, I never liked the ending, felt Joe got ripped off in the deal, his identity got erased. But as others have said, perhaps that is partially the reason this movie is etched into my mind and I revisit it around every 3 years.
I LOVE this film, and perhaps with a story book ending, it would have been just another rom-com.
Great casting and great music.