Do I ever get xp for my party member's kills?
One of the significant new differences for Diablo III is that there is no "party" system, and within a game all players are assumed to be in the same party. One of the benefits being that if you are helping another player in a game, by fighting side by side, then you will get experience for doing so.
Players in reasonably close proximity share experience
Clearly you don't get experience by sitting on your butt in town, at some radius you stop getting experience from your hardworking allies slaying the teaming masses of Hell. So if, like me, you enjoy playing a ranged class and staying out of the fray, roughly how far can you be away before you stop getting shared experience? Is the radius with respect to your allies, or the monsters they are killing?