I agree it is hard to change your mindset when you move over from Windows but as long as you are careful and watch what you are doing--especially when it comes to using your admin password--you will be fine. I do nothing special to my iMac and it runs great now just as it did 3 years ago--no malware to slow it down. You just have to get away from thinking Windows and think OS-X--just be sure to keep track of what is going on in the OS-X world here and on other Mac blogs just in case something malicious does come into play. 