I really love this film but I suppose I am not surprised that so many people disliked it. As Shuba said about 5 years ago, "Subtle, beautifully scripted and very affecting."
I thought all the characters were incredibly interesting, Sandler's especially, of course. His interactions with reality, his sisters, the bizarre, etc is so interesting. He definitely plays a psychologically fascinating character. I think this film is heartbreaking in a lot of ways, I also think its a pretty incredible love story, really funny and really brutal. It is definitely strange and there is stuff in it I don't necessarily understand but I loved it. I really never tried to figure out what the piano was about or anything else that might be "deep" about the film. I just know that there is a lot going on in Barry's life and watching what happens to him and how he reacts to it/deals with it was so interesting for me. Dunno, just really enjoyed and appreciated the film as a whole. I always enjoy it when I watch it again.