Between 1-2% of our users use OpenID. That's half of what it was a year ago and the drop has been pretty consistent even when we control for demographics. When we look at slightly-tech-savvy or mainstream demographics usage is almost zero.
What are other people seeing? What about with other options like Facebook Connect? Was there anything you were able to do to boost usage?
Here's the data I pulled from CrowdVine on this:
http://blog.crowdvine.com/2009/04/02/declining-openid-usage/