Two days ago, I forced myself to slog through Act II on Inferno. I've beaten Magda a day or so before - so it's the Kull storyline up to the Belial fight. I made it all the way to the last dungeon, where I logged out. Long session. Good progress. Yesterday night, I squeezed in an hour of Act I farming between movies.
Guess what. When I wanted to complete Act II today? Guess where the game let me continue... AFTER the fucking Magda fight. I lost like 5 hours of hard won progress (and that's a low estimate). Fucking assholes with their shit checkpoints and their shit chapters and their shit balancing. That entire fucking thing is like the worst fucking hellhole in the game, and I've got to do it twice now.
So once you've decided to progress, you aren't allowed to farm Act I anymore, lest you lose all progress? You got to be kidding me. Your brains on my angry fist! GRRRR.