We've run a session 1 this afternoon... and I'm very, very impressed.
Among 6 people present, I've read about 2/3rds of the rulesbook (stopping at setting-specific details), 2 more players have definitely read it at least partially and 3 more admitted that 300+ page book kinda intimidated them. We've spent about 3 hours in total going over the basic mechanics, describing the city of Flint for several players who didn't play in this setting, creating their characters, discussing crew type and starting position - various upgrades and their relationships with the fractions of the city. I decided to place this game near the beginning of adventure 4 (end of year 501 A.O.V.), when the constables of my main campaign shot Lorcan Kell dead in the broad daylight, which threw criminal underworld of Flint into complete chaos - perfect time for an upcoming group of daring scoundrels.
They decided that they want to run a gang of professional thieves and infiltrators, which try to earn their place under the patronage of Morgan Cippiano, who has just started to expand his operations. The crew included two Slides (poor noble scion and street circus hypnotizer), Hound ("child of the forest", only recently arriving to the city jungle), Spider (deva arcanologist, expelled from Slate University for immoral experiments) and Lurk (changeling killer for hire). They were pretty far into the game when they realized that nobody actually trained Tinker action rating to pick locks and safes, which is kinda strange for a band of thieves...
Cippiano dropped them a lead that house of recently arrested lawyer Quentin Augst has his personal archive with a ton of juicy info on his former clients. RHC was still producing a proper search warrant, so they had roughly a day to try and grab some of these papers. They whipped up a rather complex plan with simultaneous approach from street level as city inspectors, from the roof and through underground tunnels... I don't want to describe all the problems they got themselves into, but in the end they got the papers they wanted, some jewelry and magic potions for side cash, two players damaged their psyche (permanent personality quirks, Reckless and Vicious), at least two policemen are dead, and the house itself was blown to bits by Drakran experimental bomb (alpha-version of the bomb from adv.5). Yes, that kinda escalated quickly and I enjoyed every moment of it.
Best of all, it took a total of 4 hours, with about 1.5 more spent describing payoff, their next plans and overall impression of the game. I know these players, and I had absolutely zero hope that I would be able to run a complex encounter with simultaneous combat and social parts in three different places so fast in a system they've never played before. I think we'll play a couple more times in this system, and I hope I'll be able to salvage some tricks for use in my main 4e campaign, probably with healing surges in place of Stress costs.
