I really like using OpenID on StackExchange sites. I just click the "Google" button and I'm logged in!
What's funny to me is how many sites rushed to be OpenID providers, but there were not very many consumers. I tried counting once but I lost count at 15 OpenID accounts that I have from various sites. So much for single sign-on.
Do you think? Whenever I get a change to use OpenID on a website I immediately do so. I personally think it's very useful but perhaps a bit too complicated for non-tech users. Although the OpenID provider buttons (think StackOverflow) do make it easier.
Sad, I think HN was one of my last consumers of my OpenID account.