Avast FTW. My old Celeron D lagged like hell when using AVG 7.5,
and it got worse when I switched to 8. Then I used Avast, and
pretty much reduced the massive slowdowns.
How bad was it: Take Battlefield 2.
With AVG 8 running in the background: Lag. Lag. Lag. 5 FPS.
With Avast/AVG 7.5 : Extremely playable
So yes, I agree 8 really ruined my AVG experience.