To OpenID or not to OpenID? Is it worth it?

Question

Does OpenID improve the user experience?

Edit

Not to detract from the other comments, but I got one really good reply below that outlined 3

Answer 1

I have been finding more and more that if I'm required to pick a username, and my preferred one is already taken, I'll simply leave the site. At least one company has lost a sale this way, and I refuse to join Twitter. On the other hand, sites that use your email address as a username don't have quite the same problem. For me, it's a different problem: Which address did I give them?

The good news about OpenID is that a few major sites have found a way to make it easy for new users to figure out what's going on, by listing the icons of a few sites where they're likely to have accounts. Whether your average user will trust that method is still in question, though.