I use Kaspersky and have for about a year now. I hosted a Windows 7 launch party and one of the package items were a free 1yr subscription to Kaspersky IS for everyone that attends your party. I was very impressed with KIS 2010. It was light, fast and rarely bugged me about anything. It also did a very good job at detecting bad stuff. KIS 2011 is a whole different story. It is a resource hog, which isn't that big of a deal since most newer PC's and laptops have sufficient RAM to handle most anything. It is also very annoying, popping up and asking me this and that. I have changed the settings to mimimum and adjusted this and adjusted that. It also scans every single .exe when launched and takes a long time to do so and this slows any install down to a crawl. It drives me crazy. I could turn this feature off, but then I won't be protected if something is fake and installs something nasty on my machine. If KIS 2011 was as good as 2010 I probably would have renewed my subscription when it was up, but now I think I'll go to MSE. I have tried it and have put it on many families and friends PC so I know it does it's job.