my $0.02...
I just faced the same dilemma and here's my feedback on what lead me to my final decision...buying a white MB (prev gen).
First, I am not using my laptop for video editing nor am I a 'gamer'. So, accelerated video processing, while nice, probably won't be that noticable to me. I primarily use a laptop to surf the web, email, store/view pics and store/listen to mp3s. I use it several hours a day so reliability and
Things that I thought would be nice were: aluminum case, backlit keyboard, bigger memory/HD and a nice display. When I realized that the newer baseline MB (cheaper) came with 2.0GHz CPU and did not have a backlit keyboard my initial infatuation started to wear off. A few bonuses could be had with the other model but I started second guessing the value of that $300 premium.
I was buying my laptop from Amazon where older (prev gen) Apples were eligible for rebates (from $75-$150, depending on the model). So, factoring in the now reduced price for the prev. gen. model and incl the rebate the price differential between old and new became significant. The baseline (white) MB with 2.1GHz, 1MB RAM, 120G HD could be had for $869...that's new! An aluminum 2.4GHz MB would be nearly twice that price.
If I wanted to beef up this 'old' model, for about $200 (maybe less) I could upgrade to 4GB RAM and 320GB HD (via NewEgg, for example) and still save myself $100s.
Sure, the newer models are better, aluminum is better, 1067 front end bus is better, DD3 RAM is better and the newer display is probably better. But, for me, it wasn't $500+ better. I applied the law of diminishing returns and the decision was easy.
Good luck.