Basically Nothing, other than showing you either have no life or don't play as much :)
Chat with our AI personalities
aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaahhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhh
Respect from other players is just about it
No. You will not be able to keep your 11000 gamerscore that you earned with an offline account. I got f***ed myself, and lost 7000 worth of achievement's.
It is worth between $100-150
no, its just there to make your gamertag look better.