So, before patch 2.0, you chose a quest when farming some route (for example imprisoned angel), and you started from the beginning of that quest. Once you were done with your farm route, and wanted to start it again, you had to reset that quest line in order to reset all the bosses and so on.
Now there's a RESET QUESTS -button right smack dab in the middle of the screen.
Well, silly me, I thought this was the button we need to press to reset that particular quest line again. So, being on torment, having killed Diablo on inferno and thus having done the entire max level, all four acts, I clicked to reset the angel quest. I went into the game, and was confused as to why I was in act1, at the very beginning. So I left the game, went to choose imprisoned angel, and...
F*** my life!
It had reset all my quests on torment. I was back in act1, with no access to act2 or further. So, now I need to go through the entire game again, just to get my farm routes open. I know it's not a huge deal, and I know it's done relatively fast. However, I just thought I'd point it out here in case anyone was wondering what that button does, didn't read or comprehend it's tooltip (if it had any, I didn't even look before clicking), or hadn't noticed the button yet.
So... Unless you're looking to start the entire difficulty level you've selected from scratch in act1, don't click that button.