Since they're selling it with Ubuntu preinstalled, that means all the hardware is supported, so sure, that's the way to go. I would immediately blow away their install and install the latest (Hardy Heron) release of Ubuntu myself though, to get everything set just the way I like it. I run Kubuntu, which is Ubuntu with a different user interface (
KDE vs.
Gnome), because I strongly prefer that interface. It's probably more "Windows like" and easier for you to adapt to as well, so consider that option. It's all just a free download and DVD burn away, after all. That's part of the beauty of Linux.
And of course, if you have any questions with the quirks of Linux, I'll be glad to help you out. To answer your specific questions:
1. OK
2. You're all set, and there are open source alternatives for most apps anyway.
3. Yes it does, generally. I've hooked up USB thumb drives, external hard drives, etc without a hitch.
4. I play music using Amarok and don't listen to podcasts, but they would play just fine on any number of media players. The DRM stuff will be a problem without stripping the copy protection, yes.