Well, the creak is not the saddle. It doesn't go away when I stand.
However, tonight I did notice that it is not consistent -- there are times when it goes away completely, times when it gets louder. When it seems loudest is when my cadence slows and I'm ready to downshift...and if instead of downshifting I just peddle harder and pick my cadence back up, the creak goes away.
I'm going to swap pedals before I do anythign else to be sure it's not those. After that, my next try will be the BB, since that was mentioned as a creak source in another forum/review of this bike. Really annoying.
Oh, and the rear wheel is just a bit out of true now, after 150 miles of riding. I guess I chalk that up to hard downhill braking and my general fatassery. Is it worth getting a stand and learning to true it up myself, or should I just take it to a shop?