Sen. Joe Biden (D-DE) voted against Sen. Jon Kyl’s S 474, Internet Gambling Prohibition Act of 1997, a bill that passed the Senate 90-10. This is positive both because the ticket has someone who's not knee-jerk opposed to us, and because Obama was willing to choose a running mate who is not knee-jerk opposed to us.
I've rated Biden "B", and Obama remains "C". I'll likely rate the ticket B-, but haven't made that decision yet.
The guide is here.