I have made the switch to Linux for some time now, however I have only fully switched all my computers to Ubuntu Linux a couple weeks ago. I recently purchased a Laptop that had Windows 7 preloaded (a practice I think shoves mediocrity down the consumers' throats).
Figured I'd give Windows 7 a go out of sympathy, worked out O.K. for a while but one simple issue was bugging me, I kept picking up viruses on all my Flash Drives and even the digital camera had it on that flash drive, they didn't do much apparent damage (or so I thought) but were a bit nagging. I noticed a couple days later after using the Windows 7 Machine to update a few sites I did that whenever I tried visiting the pages of two or more of these sites on the net, they were blocked by Firefox for Badware. Further checks revealed that they in fact had malicious code in the header that was apparently put there by some form of malware on the computer. I immediately installed Ubuntu on the laptop after removing the bits of malicious code from my sites. I also noticed prior to the complete Ubuntu transition that the Yahoo address I used for my messenger was sending SPAM to people in the address book including my other email addresses, I checked the Yahoo login history which showed me that there were logins to my account being carried out in Belarus - a place I only know was part of the Soviet Union, made tractors and who's capital is Minsk and seems to be a quite boring place, there were also logins in Argentina. Surprising - no! Most if not all my Windows friends are sending me email with various one line messages containing links, these I noticed came from those who weren't as cautious as I am with my email usage, if malware can obtain your login information, imagine what other snippets of info they can collect about you.
Reason for my switching to Ubuntu - Linux hardly ever has viruses! Hardly ever heard of any really serious viruses affecting Linux platforms that cause much damage. Yet it seems one is released for Windows every minute. Contrary to popular belief, anti-virus software is just a brilliant way to get you to pay for something you do not need - my anti-virus is Linux. The best way to protect one's self from invasion or attack of any sort is to remove the situations that will result in the likelihood of such attacks. Buying a gun and walking around behind steel armour do not prevent invasions or make us safe from them. So, I use Linux - simple and cheap!
Unlike many persons, my life doesn't happen to be on my computers or my computer for that matter, I try my best not to store too much sensitive information on it and if I do, it is usually out of dire necessity, so if my computers are stolen or broken into I don't miss much, my credit card is stored in my wallet - not on my computer!