I do. I love it. The best feature, by far, is the 'Friends-of-Friends' list. It shows who is online from your friends' buddy lists. Easy way to find new people to play with.
The feature I use the most is chat tho. Being able to play counterstrike and then message someone playing UT2004 saying over my mic or text 'hey, come play partypoker with me' is incredible.
kudos to whoever made that prog.