Well, didn't get hardware rotation to work yet, but at least I could rotate the X server screen, so the desktop runs properly.
Of course, that's done in software, so it slows down the X Server a bit (but not as much as I thought).
Nikolaus: You mentioned you could not run a DE, only direct programs - well, probably because of portrait mode. I didn't get any panel in portrait mode as well - seems like Linux DEs expect the screen to be widescreen.
Try the attached xorg.conf, that should work.
One small bug: The screen is shifted a bit to the right, but that's only with the rotation (so probably a software, not a driver bug)
The PSX Emulator still runs fine with that rotation, as does a GameBoy emulator (Gambatte) and SNES9x.
Gambatte (using SDL) heavily slows down when scaling - cries for hardware acceleration :)
So far, whatever I've been trying, I didn't have ANY ghosting on the display! It has a VERY dark black and very nice colors.