The OpenID promise sounds good in a geeky, technical sense, but judging from their past work, I do not trust the OpenID group to build anything remotely viable.
Of course, there are a few sites which claim OpenID support but implement it poorly (such as news.yc), but that's not a reflection on the protocol.
Of course, success is subjective and relative. I see a little success every time I log in to stackOverflow via OpenId, or get a OpenId guest comment on LiveJournal.
The OpenID Foundation folks did not just bolt OAuth onto the side and call it a day. One of the key new features is a protocol that allows the ability to stay on-site within a popup or other login, rather than being redirected to a third party, then back to your intended site.
I have not read the code yet to see exactly how it's different, but it seems to strengthen the attribute exchange as well for profile-type information. Most of the OpenID providers I've used are wildly divergent in how (and how many) attributes are exchangeable with the OpenID consuming site.
Do you not see these as fruitful improvements to the protocol?
Yahoo, Google and MySpace are supporting the spanking new OpenID OAuth Extension protocol. I have this on my plate at this exact moment, I am not sure how long it will take them to support this, but for now, I found Yahoo's Contacts API to be the easiest, and Facebook's Registration/SSO to be the hardest.
This is what my todo list looks like:
1) Visit all these websites: http://knowem.com/
2) See which ones have authentication API
3) Implement them.
4) ???