Well in 3 sessions so far, we start at 9PM and end at 330 - 400 am, we have barely made a dent in the first dungeon, I assume. Some of that is due to the fact that we have 6 people in our group and 3 have never played before so we have a moderate amount of down time, but the dungeon plays very well compared to what I am used to.
We have a very good DM though(in my opinion) and he has made it very accomodating to the newbs we have with us. The encounters are on par with our level(though my 18 AC cleric did get to -3 HP's because we got attacked by a rat swarm and I had no spells left for the day, hehe)
I am trying my hardest not to go through the book(I have a tendency to ruin things for myself when possible) so without knowing whats up coming, my opinion so far is very positive and I ope it stays that way because as a group we made a decision not to switch games until the whole book is done. The only other time we have done that is with Earth Dawn, normally we switch between Mutants and Masterminds and deadlands every few months.