Hit 70 with my wizard and unlocked the new mode. The new chapter isn't super long, but it did take me 2 sessions to finish. It would have taken longer if I hand hit every nook and cranny in the areas, they're absolutely huge! Near the middle of it I was just going from story point to story point and didn't do my normal "explore everything" routine. Some of the side dungeons are massive as well and Westmarch is very impressive.
Adventure mode is fun too, and I did a Nephalem Rift last night. Found some upgrades, upgraded my artisans a few times and played with the transmog feature.
I really want to start up my Crusader next, but damn if I can't pull myself away from the Wizard long enough to do so.