It helped me win NaNoWriMo and now I do all my original fiction in it. It's simple, easy on the eyes and has a fun aura about it.
Okay, I joined while it was in Beta, so now I will always have free unlimited titles. I think everyone does, but I'm not sure... Anyway, people always say the snippets are good and all, but I rarely use them, mostly because I write everything in one 'snippet'. It was a life saver during NaNo, as it let me write on computers other than my own. It saves automatically and is completely secure. I seriously can't wait for the offline mode, where you don't have to have an internet connection. Also, if you're a NaNo winner, you get a discount on the premium!