Today, I joined Bitbucket. A friend invited me. And, I must say, I am very pleasantly surprised. I have used Github before, but I just can't get warm with git, and of course that colours the experience for Github.
However, the experience for BitBucket is also very friendly, and very simple. They even send you a welcome-email with pointers to the next steps, including a tutorial for newbies and a tutorial for Subversion switchers.
And one factor, naturally, is always price. BitBucket has the best price you can get, because it's free. Other than GitHub, you can have as many repositories as you want, and as long as you don't have more than five collaborators, everything's free.
If you're interesting in trying out a DVCS, or find a nice host for Mercurial, I urge you to try BitBucket.