Just bought Green Ronin's Player's Manual and all I have to say is: wow.
Great setting done right. I already have my players making characters, and I have successfully dug up my FASA Thieves' World modules from the 80's (along with my copy of Traps and Treachery).
Im running it in the "classic" era not the new stuff, but still a great book. Lots of nice crunch to go with the setting.
Sovereign Stone's "build up energy" magic system. In this magic system you slowly build up energy until the spell goes off. TWPM adds the concept of being able to lose energy, spectacular failures and spectacular successes to the mix to make magic even more unpredictable.
The classes. Assassin as a core class. The Survivor is a neat sort of "unbreakable" street brawler. I mean, how could a class with an ability called "too tough to die" not be cool.
Not a lot really. A faithful, crunchy, flavorful rendition of the ultimate fantasy city.