I've been using Raptr for a couple of years now, mostly to track my own progress regarding achievements and time spent playing each game.
I haven't really gotten into the competition/community part of the site, ie comparing and beating your friends' scores. I don't have that many "real" friends that use that site, so I figured there might be more people in the same situation that'd like to team up and have some friendly competition(ish) through the site.
Mostly for shits and giggles, I'm not really that competitive, but it's kinda fun to grab that one extra achievement to surpass someone else on the ladder. And since the Giant Bomb achievement links are gone and probably won't be back, at least for foreseeable future, I thought this might be a good enough replacement.