@Paul: On the virus/zombie count, it's actually the second item and not the first
that causes the problems. I recall Apples being the main PCs on campus student labs way back when I was in college (well, after the dedicated mainframe terminals) and very few PCs. The lab had a persistent virus problem, particularly something they claimed lived in one of the printers and which kept reinfecting the network. I was barely able to afford a C64, so I had no such problems.