I've wrapped lots of new GTK+ 2.4 API for gtkmm. The new widgets should be crowd pleasers. I don't know of any other list of new GTK+ API, but grepping for "since 2.4" works well, because the new stuff is strictly documented from the start.
I've just done the simple stuff now, the stuff that doesn't require much thought. Based on the gtkmm 1.3/2.0 and 2.1/2.2 experiences, I should expect lots of commits/patches now. I must think about how to hide the ComboBox's Cell/Column attributes as we have for TreeView. The UIManager stuff will need some thought too.
I looked at d-bus yesterday, and started to create a C++ wrapper. I'll wrap the basic d-bus API, but Seth's clever d-bus python bindings showed me that I should add a higher-level layer on top, to allow implementation of services and clients via derivation, although those objects don't exist so clearly in the base API. Because C++ can not find it's own methods at run time, it won't be quite as magic as the python bindings, which look a bit like Java RMI to me. But it should still be quite convenient.
Particularly now that d-bus seems to be getting an IDL, this starts to look too much like CORBA (though our C++ mapping could be more C++-like). Hopefully hp will fight to keep it simple.
My reliable Hauptplatz wireless connection has been dead for a few weeks, but life might get easier with this new gratis hotstop by the Lentos museum provided by the town of Linz itself.