Let me put it this way. Between all the free antivirus products its one of the Best.
But free products don't have heuristics so it won't pick up unknown threats like the paid ones do. if your a person who likes to live on the edge of your seat by surfing dangerous sites like porn sites, sites where you get warez then a free av won't be good enough. ^thats why the quote the best security is smack bang between your ears.
You can Mse for extra protection use Sandboxie to run you browsers in and buster sandbox analyzer to analyze the stuff in the sandbox before you recover it to your main system. It can pick up keyloggers and malware better than any heuristics because it runs it in the sandbox environment and analyze what it does and give you a rating according to its threat level. Its made by the same guy who made EULAnalyzer and Spywareblaster. Those two apps you can get as well. They're not resident so they don't eat up resources. Spywareblaster protect your system settings while EULAnalyzer tell you if a programs EULA got Spyware intentions.
Your firewall you can click on my sig there's a couple of choices plus there's a link on how to setup windows firewall if you use that. There's some things you can setup with windows firewall that helps you to inform you if there's something suspicious on your pc because programs are not allowed to call certain modules of windows only malware does it. So it can be blocked by default.
Use a app like malwarebytes to scan your pc once or twice a week. clean out your junk files regularly it makes scanning and your av task much lighter when protecting your pc.
Java update it make sure you uninstall the older java version first before applying the new ones. Adobe update it. Not just the plugin but the reader and writer from Adobe as well. That's where click jacks and rogue malware get thru. Thru old exploits of java and Adobe.
All that stuff I mention is not things that eats up any resources or make your pc slow as crap. Its just a lil bit of weekly maintenance of your pc to help your av out.