MSE is as good as any costly alternative in my opinion.
Having said that I no longer use antivirus software, I find the pop ups annoying and the scans seem to take forever as well as adding to RAM.
I believe that if you are careful as to what you open and run in e-mails or internet pop ups etc you will be fine. I do however have back ups of most of my most important files and I am wary of who I do business with online!
I am yet to run into any bother, you could call it luck but i disagree
HAHA spoken like my best friend a year ago, he said he was the carefullest and smartest person about not downloading or running malicious files, but when got his WOW account hacked from a trojan that was put on his computer i just sat there saying I told ya so and he changed his mind about virus protection that day he lost everything. No one is impervious to viruses, and those who think so need to learn that the hard way.