I voted this up... After creating an account and commenting on the idea I was reading at the time I decided to sign up, this is the first thing I searched for. I find it very annoying to have to maintain three accounts for the three things I am likely to use most in Ubuntuland-online.
Single Sign-On PLEASE!
However: It does tno have to be OpenID... I guess that many people (including myslef) would prefer this to be an ubuntu-centric single sign-on. Honestly, I don't know what to make of the OpenID thing just yet and am not ready to commit to it. Sometimes I don't want my identity so easily correlated across the web. When chosing between living under a rock and wearing a tin-foil hat, I'll take mine shiny-side-out please.