I use AVG security software (full-blown version, not the freebie). I switched from IE to Chrome twice. Chrome was quick, but both times I got virus attacks within a day or two, and once I'd sorted that out I went straight back to IE. I never have any problem with viruses using IE9 with AVG. Might all be down to coincidence, but I'm not pratting about any more. You can keep 'em all, I'll stick with IE.

IMHO, YMMV etc.