I work on computers for a hobby. A lot of the time I just need to remove a virus or speed up the computer. One of the things I find most annoying is when people have a virus, but they have an antivirus subscription that they paid for! Another annoyance I have is when people have an antivirus program that is slowing down the computer a lot and they wonder why the computer is slow.
The main antivirus programs I have seen that do almost nothing but take money are AVG and McAfee. My usual solution to a computer with AVG or McAfee with a virus is to install Microsoft Security Essentials for free and remove it that way. Then I strongly suggest to the user to uninstall the previous antivirus even though their subscription isn't done.
The other issue that's not so big is slow computers. The main antivirus that I've found to cause this is Norton. You might think it's a great deal that your ISP gives you a subscription to Norton that usually costs. The problem is Norton is such an inefficient antivirus that slows down computers a lot. I have found it to provide no more protection over high-quality free antivirus programs. Norton includes a firewall; that sounds like a great thing, but I have found no advantage of it over the built in Windows firewall. The only thing it does is slow down your computer and use up space. Do you expect the software developers at Symantic to know how the Windows network interface works better than the developers at Microsoft who integrated the firewall directly into the system?
In my experience working on removing viruses from systems I have found Microsoft Security Essentials to be faster, easier to use, and better at the task of removing viruses than McAfee, AVG, Norton, and most other free and paid antivirus products.
In the world of antivirus programs paid does not mean better quality.