40d14 on XP64 (latest service pack/patches), an old save, with only Mayday's changes to the raws copied over for save compatibility:
The game has horrible slowdown outside, but more perplexingly, stops screen updating when I try to move the screen when it reaches a central stairwell with hatch covers next to a bottomless pit. If I hit escape, and return to game, the screen recenters where it should be, but won't refresh unless I do that. Moving the map focus anywhere else on the map -except- for the stairwell is laggy, but functional. I think it's more the chasm than the stairwell, but can't really tell for sure.
If I actually edit the init (and no, I didn't copy the old init over, I always manually update it), input lag becomes too great to even launch and load a save, much less play. And all I am doing is pointing the init at the tileset, not changing anything like partial print, etc.
So far the quickest and most stable for me has been d12, and I am looking forward to d15 because these speed and functionality improvements you guys keep offering are awesome. Keep up the good work!
e: after another attempt at adding in elements one at a time, I think that I can say the severe refresh lag hits only if I try and bring the bottomless pit onto screen. I've got tiles working now as expected (no performance difference with or without, using this same save).
e2: trying to worldgen with this current setup was a horrific idea, even at realtime priority on my phenom 2.