Honestly my biggest bug bear is the automatic pop up advert when I simply press the “login” button after navigating to the site. I pay for a membership which is supposed to be ad free, circumventing that by forcing a pop-up-in-new-window advert before logging in is a bit underhand.
Membership has never included an ad-free experience, so there's nothing being circumvented. In fact, there are three ad positions on every page of the site, so it's hardly a secret that advertising is part of how the site operates.
As for the login advert, it appears before you've logged in. Until that point, the site doesn't know whether you're a member or not, so there's nothing remotely "underhand" about it.
It's perfectly fair to say you don't like the advert. It's much harder to argue that it's somehow depriving you of a membership benefit that has never existed.