Not having a go Kezzer, but i've heard some people before saying they don't need AV because they know computers well, so do i, but better safe than sorry, but still.. it's not like you can tell if you download something off the internet and know if its a virus or not, well i guess it depends, but in some cases you may not know.
Anyway, better safe than sorry i say, even if it does slow my computer down a little .