I got the 2.4 Uni MB and I love it. But that probably goes for either, they're brilliant. A lot of people are going to say that the upgraded 2.4 is not worth $300 more, I thought it was. Even though I don't need the backlit keyboard, it's cool. The extra HD space will help me out someday, but by then HD's will probably be cheaper. If you look at benchmark tests between the 2.0 and 2.4 MB, with like rendering and stuff, you'll notice that the 2.4 is about 5-10 seconds faster over about a minute and a half. Is that worth it? That's up to you.
I bought mine on Amazon and there it was only $150 more than the 2.0 MB, so that was definitely worth it.
Hope this helps
IMO the larger HD of the 2.4 is irrelevant because the HD's are so easy to change, and large capacity, high rpm drives are so damn cheap these days. I paid $85 for my Seagate 7.2K 320GB drive.
I say the money is better spent maxing out RAM and getting a bigger HD from macsales.com.