Love this plugin/service.
It's the only working single-sign-on (SSO) method allowing users to "connect" using the "Steam" network that I have found so far.
Everybody is putting a lot of emphasis on FaceBook, Twitter and other social networks. But, "Steam" is going to continue to get bigger. It is quickly becoming the leading PC-game distribution platform. So, it is a built-in audience of people who actually buy and software/games - not just random people who (just) want to stroke their ego's on-line.
A great option for anyone targeting PC-gamers. Don't make them register using built-in functions, don't make them use a face-book - they already have Steam to play Counter-Strike, TF2, etc. - let them use that!