I put in an order for one of these guys too. Mine isn't supposed to arrive until early july though. I'm pretty familiar with linux and programming and once I go down that road, I should be able to help you out.
If I were you, I would definitely stick with Ubuntu on it. The Sheeva plug does not have an x86 processor in it. It has an ARM-based processor. Therefore, if anything you put on it needs to be compiled for ARM. There are several operating systems out there designed to run on the sheeva plug. I like FreeBSD much more than linux, so I MIGHT use it instead of Ubuntu. The sheeva is powerful, but I would hate to compile an entire linux distribution on it. It might take days. So ICE as far as I know, is not compiled for the sheeva plug, not even ARM for that matter which leaves it out of the question. Theres a list somewhere with the operating systems that will run on it.