I'm sure Biden received a very thorough physical before even beginning his own Presidential campaign last year.
It's par for the course and very doubtful that any health issue would sneak up on him this late in the game.
Also, FWIW, Palin was picked as a direct response to Hillary not being picked. Had Obama picked Hillary, McCain probably would have picked someone else who would have helped him in other ways.....and a bunch of people would be here debating on how Obama should have picked someone like Biden.
