I have rejoined the Avast users after quite a long absence (I have just purchased a three-year licence for Avast Professional). I had been using other AV products, but decided to ditch them for a variety of reasons, such as:-
Kaspersky – the latest version gave me several false positives and they seem to have removed (or at least hidden) some of the options in the new version, such as being able to be prompted when a suspect file is found. The previous version caused my PC to freeze at random intervals.
Spyware Doctor with AV and Webroot Spysweeper with AV – both of these slowed down certain programs on my PC to a crawl (especially IncrediMail).
Bit Defender – Completely wrecked my PC setup (fortunately, I had a recent disk image made by Acronis True Image, so I was able to restore my PC back to a recent configuration).
Avast seems to be working fine (apart from an initial false positive, which has now been rectified by the developers), so I am completely satisfied. Best of all, there is this very active and knowledgeable support forum to consult with others users if and when problems do occur.