Last time I looked at dotcloud, I found two services in the free plan to be not sufficient; I need at least two (perl, postgres), and another for caching as soon as I get some noticeable traffic.
Anyway, I'll keep it in the back of my mind, maybe I'll try it eventually.
I'm still a bit too old-fashioned and cheap for cloudy things, but the easy of deployment still helps if you run it on your own server.