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 advantages of OpenID in a rational bottom line kind of way. I've also heard some whisperings in other comments that you can get access to some details on the user through OpenID (name? email? what?) and that using that it might even be able to simplify the registration process by not needing to gather as much information.

Things that definitely need to be gathered in a checkout process:

• Full name
• Email

(I'm pretty sure I'll have to ask for these myself)

• Billing address
• Shipping address
• Credit card info

There may be a few other things that are interesting from a marketing point of view, but I wouldn't ask the user to manually enter anything not absolutely required during the checkout process. So what's possible in this regard?

/Edit

(You may have noticed stackoverflow uses OpenID)

It seems to me it is easier and faster for the user to simply enter a username and password in a signup form they have to go through anyway. I mean you don't avoid entering a username and password either with OpenID. But you avoid the confusion of choosing a OpenID provider, and the trip out to and back from and external site.

With Microsoft making Live ID an OpenID provider (More Info), bringing on several hundred million additional accounts to those provided by Google, Yahoo, and others, this question is more important than ever.

I have to require new customers to sign up during the checkout process, and it is absolutely critical that the experience be as easy and smooth as possible, every little bit harder it becomes translates into lost sales. No geek factor outweighs cold hard cash at the end of the day :)

OpenID seems like a nice idea, but the implementation is of questionable value. What are the advantages of OpenID and is it really worth it in my scenario described above?