>I run MSE, I barely notice it speed wise, and haven't had any malware or viruses.

I run several things on both Windows and Mac. The Mac version feels a lot faster. If I shut off all the virus stuff the windows stuff is still slower but not as dramatic. It depends on what the code does, obviously. Any disk or network read/writes take a hit so if you're doing a lot of those it really adds up.

>Strongly disagree; if you look at this MacDefender issue, there is no flaw in OSX that is causing infection, users are installing it on their own accord.

The solution to this is what Apple has already started doing: provide just one place for these kinds of people to get software. Just buy it in the App store. That is the proper approach to "protect users from themselves", not put a 20-30% performance penalty on all Macs.