I've got 2 GB on my iMac and noticed a performance improvement from it not swapping out to disk all the time(it had 256MB when I bought it). You'd see an even better improvement by not swapping out to a slow laptop drive.

I've notice my system using 1.2 GB before, and I'm not running a virtual PC environment.

[link|http://eshop.macsales.com/|OWC] has [link|http://eshop.macsales.com/MyOWC/Upgrades.cfm?model=214&type=Memory&TI=%23TimeFormat%28Now%28%29%2C+&shoupgrds=Show+Upgrades|PowerBook memory] for quite a bit less than Apple. From Apple you'd spend $850 for 2GB, it's around $300 for 2GB from OWC. I've purchased all my Mac memory from them(along with CPU and CD burner upgrades) and haven't had any issues.