Just a quick update, everythings going smoothly.
Even with 512Mb of RAM, I'm still managing having a few apps open at once etc. I can happily go along with Finder/Dashboard/Safari (3 windows)/Messenger (3 windows)/Limewire running, and switch between them quite well. I'll definately up the RAM to 2Gb when I can though, but for now it's doing perfectly well.
Temperatures: could use on my lap, though it does get a little warm sometimes, but I tend to use it on a desk. No signs of dicolouration, no mooing, i think a couple of times I hear the "idle whine" but it just sounds like a very faint beeping, and to be honest, even in a very quiet room, it's hardly noticable.
Ambient temps (according to Temperature Monitor) are usually between 48 - 56ºC, but its usually settled around 53ºC. After playin Marble Blast Gold for half hour, I finally heard the fan going. So I quit, checked TM, and only had a temp of 65ºC.
I'll try the 'Terminal Test' now (yes >/dev/null) and see how it goes.