I'm NOT against a "balanced" advertising. Avast is still a business I think that, in this case, Avast Software made a mistake.
When the user updates the program, several things could go wrong. The user either throws Avast out, or searches for help / solutions / workarounds.
When Avast Software decides to include, AT THE SAME TIME, some additional changes, it can only stress this "glitches" (or potential bugs) a little more.
The one-time advertising (screen notification) is not the only thing that was included at the same moment of the program update (to 6.0.1289). Avast Software decided to include the possibility to upgrade to AIS (15 days free trial), and to give also the possibility to go back to the usual Free edition. This, IMO, was NOT smart.
Updating the program is enough "stress" for the rare cases were something goes wrong. All the advertising and 15 day trial needs to be separated from the program update process. It "might" be less successful as an advertisement campaign (or not) if it is separated, but for the users, it is much more reliable, simple, and stable.
Under the current situation, users having problems "just after the program update", need to investigate "more than usual", to find out if the program update was the one generating the problem, or was the ad notification, or was the 15 days trial, or was the "going back to the Free edition".
All this "extra stress" was (and is) unnecessary, and avoidable by simply separating the campaign from the program update.
Once Avast's servers detect most (or all) users have updated the program, only *then* start the campaign. This gives time, for the users that indeed had problems updating the program itself, to solve any problems and to give enough feedback to Avast Team. Only *then* start the campaign, that might bring other users with other problems to resolve, but the trigger of the problem is much more narrow than under the current "program update + simultaneous ad + simultaneous 15 day trial + option to get back to Free edition".
This means an additional “program upgrade” (or edition upgrade, I should say), but IMO it is less problematic than the method used while updating to Avast 6.0.1289.
As I said, unnecessary stress.