Well free is best in a lot of cases. I made the mistake of buying Spyware Doctor, and it bogged down my system when my computer started. It released resources after about 4 minutes. Hopefully I'll get a refund.
I don't like to buy software unless I can "test drive" it for awhile. Because if it won't work right, that's money down the drain.
and all the free programs I use, they do have paid versions. But why buy the cow when the milk is free?
I use, in addition to A2 malware scanner:
1. Spyware Blaster
2. Adaware
3. Spybot Search and Destroy
4. PC Tools antivirus
5. Malwarebytes
But I do not have any except No.4 running in my background. Never got anything nasty in a long time. I surf the web, with scriptng disabled,(Firefox NoScript) except on sites like this.
What backgrounds? I'll have to see if I can find them.