SK has a downloadable client too which is way faster than loading from the web at least it is for me, though Steam does offer some great features though, ability to take and upload screenshots directly to their cloud service, overlay browser so you can look stuff up while playing without having to alt+tab and other stuff too, I think it's great that it's on Steam I've been using Valve's service for years have over 200 games on it in fact SK was one of the few games I play outside the service so it'll be a nice addition ONCE they link our accounts if ever.

*edit* supposedly the overlay is not available that's a bummer but still there's other good features.

Don't forget voice chat. I've been hearing people breathe and they had no idea their mics were on. Dishes clanging, children yelling. Steam voice is on by default and no one seems to notice.