People often complain that an AV constantly shows them some notifications in the form of promotions/upgrades, or informs them that a threat is blocked - but this is very easy to turn off in the settings. It took me less than 10 minutes to go through all the settings and set things up the way I like, but I believe a lot of people have problems with stuff like that.

No matter what, there will always be pros and cons for AV on your PC, but if you choose the best possible AV with a solid device configuration, I think the benefits far outweigh the disadvantages.