I'm still new to the game myself, but I enjoyed the short time I played.
I don't know how long the guest passes last. I guess we'll find out when I send you a pass.
EDIT: And I have no idea when I'm able to play anything other than TF2 (Tuesdays), L4D2 (Wednesdays), UT3 (Mondays), and LoL (every other Thursday) these days. All other gaming tends to be at random times when the baby is asleep.