I bought a 2.2GHz MB, instead of the 2.4GHz (2nd last revision of the white plastic macbooks). To be honest, after using mine and trying out my friend's 2.4GHz, there's not much of a difference apart from maybe a few split seconds quicker in say, rendering something in Photoshop. Mine was upped to 4GB RAM, while his was stock 1 or 2GB 😕.
For this 2.0 you're talking about, I assume that it's the plastic white MB vs the aluminium MB; my MB is already lightning fast, and they've even updated the plastic MB recently (I belive the FSB too), so 2.0 should be enough.