Yeah I haven't actually tried, but I do know my monk went through WAY faster than my warrior, though it was also twinked a bit.Act one is probably the quickest of them all - probably takes 30 minutes roughly. The zone layouts change, but.. not really. Especially if you're not going off the beaten path to get the passive bonuses from shit. So you end up going from boss, to boss, to boss in quick succession. Which is especially timely if you're so good at dodging their mechanics that you can still kill them when you're under leveled and under powered, respective to the upgrades you get along the way.
If you really think about how much we've learned about the game, what works, what doesnt work, what defenses to build and which ones to completely ignore... I cant imagine anyone that went through the early release cant get through acts 1-3 relatively quickly. Though, 2.5 hours is still booking it - on a mission type shit.
If the update with wipe ever happens maybe Ill try to rush through just to see what I can do on a fresh char. Though I won't be skipping the extra passive skills or resists either. (Not sure if they were taken in the race)