Steam digital distribution system has exceeded 15 million users, a feat that is most definitely worthy of cake.
In addition, an official press release states that Valve has seen 158% sales growth over the last holiday season, putting the company in a pretty good place coming into 2008. Steam's rapid growth is likely due in part to the critical success of Portal, as well as the ever-expanding offerings available through the download service.
With last year's debut of the Steam Community features, and the zombie survival FPS Left 4 Dead coming later this year, we can only anticipate that Steam will continue to grow in popularity. Kudos to Valve folks for all their hard work. Now, can we have a Mac version yet?