For me the reason I doubted the popup was that it don't resemble anything I've seen from Avast! so far. And when it started popping up, topmost window btw, three or four times a day I thought I might have a virus. Anyway, no biggie as I got my answer from these forums straight away.
Eric March:
It is a good way to get the information out. But it is very important to ensure that the end-user knows instantly that it's coming from a legitimate source, especially since it's a form of popup you can get a lot of from shady websites.
I've seen a lot of popups from Avast! that all have a very different style, and that prompted my first reaction.
The second problem imo is that the popup is very large, always on top and appears 3-4 times a day and that only during the 6-8 hours that I spend on my home PC. If the older version will be supported until the end of this year it is too much or rather too soon to spam that big a message that much.
There is nothing wrong with the information or the offers, it's the way they are presented.