The honeymoon is over and now we are getting to know each others foibles and learning to get along just fine.
The most incredible experience so far has been running some very heavy lifting Jython-based XML processing pipelines in the background while still working away in Emacs, downloading e-mail and surfing the Web.
The Jython stuff goes noticeable faster than it did on my old Dell/Windows setup. More importantly, it does not cause the machine to break sweat. I can do other computationally intensive things in other shells at the same time.
Fantastic! How much of that is down to the fact that the Thinkpad T42P is one honkin' laptop and how much of it is down to Ubuntu/Linux I don't know.