I downloaded the new Sharepoint 2007 SDK today, published last week though it's dated from April 2007. There appears to be no change history for this version of the SDK.
I was hoping for more information on new Web Service methods available in 2007 - hoping that the lack of 2007-specific functionality was more of a documentation error than an actual oversight. It seems this is not the case.
I've written about the lack of item-level permissions in the WSSv3 web services before, but I've found some other serious problems.
Documentation-wise, the new ChangeLog methods (GetChanges() in various web services) remain almost entirely undocumented.
The Permissions web service, like the previous problem, seems entirely unmigrated to WSSv3 and remains identical to the WSSv2 version. The painful point for me right now is that AddPermissions accepts a 32bit integer for the PermissionMask parameter matching a value in the 32bit SPRights enum - even though WSSv3 marks that enum as Obsolete, replacing it with the 64bit SPBasePermissions enum. This means I cannot set permissions to any of the extended values via web services, only via the object model.
In short, I am quite disappointed with WSSv3's web service support, and even more with the documentation. I get more information from the WSDL at http://myServer/_vti_bin/sitedata.asmx?op=GetChanges than I do from the documentation, and that's a shame.