At v0.5, I've been using the QxtRPCPeer class to send signals/slots over TCP/IP, and with one small fix, it works flawlessly.
I've yet to check out the rest of the library, but there are some real gems in there so this should definitely be a part of most Qt-developers toolbox.
A central place where useful Qt utilities can be developed, outside of Trolltech, is a good thing that needs support.
We likes it! ;-P