N900 was a great deal closer to a PC OS than any release of Android I've seen past Android 2.x. It even has X11 and a built in, honest-to-goodness version of apt! You can't say that about many phones these days.

I'm almost sure that with enough swearing and elbow grease I could replace the entire GUI with something that I can write myself to be tailor-made to my needs. Doing anything even close to this for Android seems like a daunting task.