There is a difference... whether or not it's noticable to to depends on how much you push your computer in daily tasks.
There will definitely be less "spinning beach balls" with 2 GB vs. 1 GB. That being said, I have a MacBook with 2GB RAM and a Mac Mini with 1GB RAM, and in daily tasks (surfing, iTunes, Movies, DVDs, MS Word) I notice little difference in responsiveness between the two.
In my opinion, 1.5 GB is the minimum "sweet spot" for any new Intel Mac. I've witnessed noticeable performance improvements on a couple of iMacs which were upgraded to 1.5 GB and 2 GB. But it's hard to notice any significant difference between the 1.5 GB and 2 GB machines, although none were put through any "difficult" tasks.
Considering the currently low price of RAM, I'd be more inclined to opt for 2 GB or more.