I'm 4 hours 18 minutes in and I'm still in Act I. I think I'm at the final dungeon. I've been taking my time and exploring everything, talking to all the npcs after quests, and soaking it all in. I'm in love. The game is awesome. Playing a barbarian btw.
My brother and I are around the same area with the same amount of time. All the journals and lore really help to flesh the story out. Game is beautiful too.