I've mentioned before in previous snickerblog posts that the reason why so many games don't even boot in WashingtonDC is that I've yet to implement the AICA audio hardware. I'm working on getting that done in the snickerbockers/aica_audio branch over on github. On that branch, I recently implemented sample timer interrupts which go to the ARM7, and that has unblocked at least three games. Jet Set Radio, Space Channel 5 and Skies of Arcadia are now in-game on the aica_audio branch. Additionally, the full SoulCalibur intro movie now plays. Previously, it would end prematurely after the camera goes over Mitsurugi's shoulder during the first shot and then go straight to the title screen.
There's still a lot of stuff unimplemented in this branch, and it doesn't actually play audio yet. I think this will get merged to master when there is working audio even if I don't have all the AICA hardware implemented yet.