XML? Sure, follow the hype.
Unless you want performance.

I watched a demonstration at a VBUG seminar at MS Reading, and the n-tier XML example was 9x slower than dual tier using ADO.
That's even on the same machine - no cross machine calls, only interprocess and the serialisation and deserialiation involved in XML.

With what we have today, to use XML you have to keep the messages small to keep peformance.
In the future those bottlenecks will probably be addressed.