imo macs are awful so my views are very oen sided. I used macs at college for graphics and i thought they were awful. Slow, crashed frequently and generally couldnt get much work done on them.
I also remember seeing a comparison of a computer and a mac in terms of hardware performance. i think the equivelant of a £900 was a £300 computer.
Now, to try and drop the prejudice a bit i would seriously recommend lookign at windows 7. It really is ace, vista was shite. If you dont want to take an interest in your pc/mac with virus checkers and stuff accept that you will get viruses and lose lots of data. Its like not insuring your house/car, only do it if you accept the consequences in advance.
Also 3 computers in 9 years is really very good. If you are a serious user expect your harddrive to die EVERY 12 months, have a backup on the go and switch them out. They really arent expensive. This will affect both a mac and a pc so it doesnt matter which route you take.