I'm not aware of any public documents, but I ran a diff across the code base and came up with precisely no differences at all...!
YMMV, but seems identical to me.
Sent from my iPhone
I haven't seen anything published that lists changes to the API.
The new CWP documentation has been updated to reference WebDirect in certain places, but that's the only changes that I spotted in the document. Everything else appears to be the same.
Also, I just discovered that you can use the old "12" version of the API to access databases hosted on "13" servers. So while I can't say for certain that nothing has changed, it sure looks that way.
I got a confirmation at DevCon (wink wink nod nod) that there will be little impact on PHP... like 'nothing'.
Obviously their challenge was Web Direct and CSS so I am assuming I will see no issues. Yet to test...