Just to see how much the apsire one can handle, I made a point to use it as much as possible. I left my desktop turned off for a few days, only turning it on when I needed the printer online or to retrieve a file that was stored on the desktop. Today I am back on the desktop, as I needed to login to a message board I am admin on and delete several posts in a single thread. This is something I could do with the Aspire, but its far easier with a taller resolution and a standard mouse.
I had 6-8 tabs opened in firefox all the time, I was streaming large WMV files through Revision 3, and had AIM running with up to 6 IM's going on. The only thing I really missed going from my desktop to the netbook for a few days, was the dual monitor display. I am so used to having firefox on the main display, while all other programs using the second display. Also when I am working in multiple folders, or following a writeup its nice to spread the work out over two monitors. So I was having to Alt-Tab a lot more then what I am used to these days. Overall the size of the screen does not bother me to much though, just requires a little more scrolling.
Anyways the size is what you should be looking at if you are considering one or the other. Also do you need to have a CD drive? Is this a secondary computer?