The recently released Tumblr app for iPhone is not too shabby at all and is hopefully a step in the right direction for Tumblr on mobile.

On the flip side, the Facebook mobile experience is pretty terrible as well, but Facebook already has quite a large (and growing) user base already, so I wonder if mobile user experience is as important to growth as is existing, for lack of a better word, penetration.

EDIT: Just noticed this line from the post: "The Compete numbers are US only and desktop only."