I've used it on numerous systems (Win98, 98SSE, NT, 2000, and XP) and it has been great. It has always been much less problematic than Symantec products were for me and I have found no incompatibilities. It runs fine with Seti 😀
As well, they seem to put out updates almost every few days now. For the most part, you don't need to reboot after updates if you are using nt, 2000, or XP. It has always done well catching viruses for me, as well. I'm referring to the free edition - i've seen a few reviews of the enterprise edition and it was spoken of favourably.
I guess this is a pretty glowing report but I've always been very pleased with AVG. 🙂