But it is NOT upgradable. :evil:
This is one of the important characteristics of macs. To oversimplify - a mac is used like a phone, tv, car. Ever desired to "upgrade" one of these devices? It is meant to be a simple device, both hardware and os.
The PC and windows world has a completely different approach, crawling under the table pulling plugs and cables and have the box open constantly to plug/check/try hardware is cosidered a big part of the fun. And a chaotic os is accepted - the folks love becoming experts in hardware and os specific stuff.
Once I fell for that upgrade myth, but soon found out that it just isn't worth it. Buy it, use it as long as it does the job - and then shell out some 399 and get the next one. And since i do serious work with it, I lost very soon the joy of constantly fumbling and experimenting with hardware, and switched to using notebooks.
Memory upgrade, that will be a very useful thing for all computers. Fill it to the max, then close the box and never again lose a second of your time with screwdrivers. The mini has 1GB max, that should be fine.