Security issues don't affect me now. I have good, professional (not freeware) virus protection firewall that is always-up-to-date. I also keep my OS and other software up to date. Certainly choosing an alternate browser doesn't mean you don't still need to do that.
Never say never. Remember, someone has to get infected before the software guys can write a virus definition.
BTW there's several freeware AV's that work well, AVG for example. Throw in a good firewall like sygate and you're not doing bad.
As a geek that spends a lot of the day dealing with customers that won't run any kind of protection I can say that there's no reason logically of financially to go unprotected and you hurt others as badly as yourself. We've begun disabling customers that are infected till the clean themselves up.