I’ve just upgraded the memory on my iMac from 512Mb to 1Gb. and it was amazingly easy.
Just undo three screws that hold the back of the iMac on, remove the back, pop out the old memory stick, pop in the new sticks, replace the back, do up the three screws, cross your fingers and switch on. It works.
Having built many PCs and seen teh insides of even more over the years the insides of the iMac are a work of art in comparison. No wires, none of those awful flat HDD cables – all very elegant.
Tiger works OK with 512Mb but with 1Gb it feels much smoother.