Tabula Rasa
I know... you're thinking the same thing I thought when I read it... What the hell does that mean... Well Ross at nCircle provides the definition, "A clean slate; a blank or erased tablet." He also provides a short, but interesting post on the subject of backwards compatibility. The ultimate question of his post is summed up by the introduction:
Backwards Compatibility. I'm hardly a Mac user, but from what I've heard, they don't bother with it. Every Mac OS release is a clean slate (or close to it) and the end user just has to adjust. On the other side, Microsoft spends millions (billions?) making sure that you can still open that document you put together using Word 95 in Office 2007.
Which approach is better? Define better.
Give it a read and see if you agree.