I completely loathe and detest ads, I really do. But I nonetheless must defend Avast's right to stick that advert there. Yeah, it annoys me, but is hardly an in your face nag screen that bugs you. You only see it when you open the On Access protection.
For a lot of people upgrading to the pro version is just not an option or it isn't going to happen. So maybe being able to hide the ad by selecting a check box might be a better idea. Or even better, integrating a 'news' and banner window there to make it more functional.
It is irritating when you see it, and I sometimes accidentally click the pesky thing, but then that's me (I don't even watch commercial tele or listen to commercial radio with ads because they irritate me so much), but I definitely don't see Avasts ad as a big problem and I certainly wouldn't slam Avast for trying to promote their Pro version. I'm grateful for this nice bit of kit.
After switching from AVG to Avast Home I'm a very happy user indeed. I wish I'd switched a long time before.