I finally got around to watching this after reading the book some time ago.
In terms of the Oscars, I think its Bradley Cooper's best performance to date, but I believe there are one or two more deserving Best Actor nominees (Joaquin Phoenix in particular - although I'm pretty sure he doesn't stand a chance this year).
Jennifer Lawrence was great but she'll have stiff competition from Emanuelle Riva and Jessica Chastain. She has a better chance than Cooper though.
I don't think Robert De Niro was particularly Oscar-worthy in this role, although I did enjoy his scenes with Lawrence.
All in all, a really great film, but there is a danger of it being completely overlooked at the Oscars.