Just Brought a Inspiron Mini 9

[gallimaufry]

Did you test if there was any noticable performance gains by increasing memory? I got a feeling that Linux is very good at utilizing "spare" memory, but I've never seen any numbers for that.

Which (if any) desktop enviroment do you use?

Nope, no tests. Truthfully, I don't think the extra memory makes much difference, at least for my use (web browsing, mostly, and listening to music). I occasionally run "top" just to see how the machine is doing, and it always seems to be humming along smoothly, getting nowhere near system limits in terms of memory usage or CPU load. YMMV, especially if you want to use it for gaming.

I'm using KDE 4.1 for my desktop environment.