It is the most ridiculous excuse for a piece of software I've ever seen. I despise it. There is nothing good about it except that it will manage the games, but, unfortunately, long before Steam we had (and still have) something called icons, which worked much better. It used to start when my computer started but that lengthened my startup time by about two, so I decided to turn it off. Now, whenever I want to play Half-Life 2, it takes a good 2 minutes to load everything.
Sorry for the rant, but I've always wanted to rant about Steam.