Chad hits the highlights -- well worth a read, as it has elements of both witch doctor and apelord in action:
http://chadu.livejournal.com/688777.html I continue to enjoy the flashback device -- for one, it lets us get outside the city in our otherwise "locked up urban" setting, and for two, it really helps to build the backstory for each character, one at a time. Low-bookkeeping supporting cast rounds out the flashbacks such that everyone gets a chance to do some awesome. And, we got to have a "low-risk" fight with a young black dragon -- the first solo-creature fight of the game.
I also got to establish how the sewer system underneath the giant towers are maintained: there are gelatinous cubes moving around through them as "pipe-cleaners". I used my sewer map tiles from Paizo to good effect, here, with platforms that everyone had to stick to unless they wanted to get down into the difficult-terrain muck. But I added a little bit of extra threat by making the gelatinous cube immune to the slowing effects of the muck -- essentially doubling its speed against some PCs (a good thing, given that those things have a speed of 3). Gelatinous cube + home turf advantage = really interesting second-half of the first post-flashback fight.