Ahem. I found one of the major slowdowns I think. The UI layer was rendered as many transparent tiles which acted as mouse targets for recentering the map. Rather than rendering to texture, I just removed the layer's rendertree() call. The input handler uses visibility, and will nicely ignore the lack of actual rendering invisible tiles...
Release mode back up to ~360fps, with all the timer/counter profiling still enabled.
[edit: Current state, for screenshot monkeys.]
I'm tripping like jesus in the desert when he fasted,
Like it's the night before we all get drafted,
Like we're rowing through some rapids with Kevin Bacon, white water rafting
Like you're on epcot center on acid?
Exactly.
-IV