I use Nod32 anti-virus only, not the suit program. And for IE and testing unsure or trial programs, I use sandboxie to sandbox it.
Few weeks ago, before I got NOD32, I was browsing some random website with IE running in sandboxie, a page popped up with an unclosable window telling me to for me to pay and enter the verification code to unlock the window. I use sandboxie to terminate the sandboxed IE and cleared the sandbox contents, then reopen IE and all is fresh and new. Highly recommended!
For some time I used Microsoft Security Essentials on Win7 and the Defender on Win8/8.1. So on the SFP3 it will also be only Defender. I never had a virus problem. But ok, I´m not using warez or surfing on suspicious websites.
I was 100% happy with Windows Defender but needed something better for my sons Windows 7 desktop.
He is a clicking machine and has zero computer safety awareness. A recent malware scan on his PC listed somewhere in the neighborhood of 120 infections.. YIKES!
I decided to just format his PC and start fresh. I tired several anti virus programs for a few days each and ultimately decided on purchasing Webroot. Since it came with a license for 3 PC's I also tossed it on my SP3.
I think Windows Defender is fine if you don't go crazy on the PC. If you have suspect browsing habits, then something more powerful might be a good idea..