<p>Currently reading quite a heavy WCF book. I have used it myself in production just the once, using tcp, worked a charm.
Anyway what are your opinions on this technology, is it here to stay, is it worth the time invested learning all the complex features etc etc?</p>

I think it is here to stay.  It is easily configurable for moving endpoints, it seems robust and allows you to do (pretty much) everything you could do in web services and remoting without the overhead of separate implementations.
I can see where you are coming from, with MS's recent leaks about ongoing support for, and maintenance of  Linq to SQL, but I see WCF as a different beast altogether.  This is a technology that allows interoperability, as well as de-complixifying (I know this isn't a real word, but it should be) communications between systems.