Does anyone have any tricks to speed up the time it takes to test and iterate on your work? I tend to spend a few seconds changing values in the script or level, and then a few minutes building bsp and the fast file. Are there any tricks you guys have to detect errors in the script before you build it, like in Ultraedit? Is there a way to speed up the BSP build process beyond turning off light building?

like, for instance, is there a way to be able to make changes to the script while the level is running and to see those changes on restart?

Light tweaks while in developer mode.
/r_lighttweakambient
/r_lighttweakambientcolor
/r_lighttweakdiffusefact
/r_lighttweaksuncolor
/r_lighttweaksundiffuseco
/r_lighttweaksundirection
/r_lighttweaklight

The only one i know that doesnt work is the ambient tweak.
But others you can make adjustments while in game, just write down
the new adjustments to add to your worldspawn values afterwords.
Open consol while in game and type r_lighttweak and the list will drop down.

You can use fs_useDevDir dvar if you're making script changes -- can change script and then devmap your map to load the changes without rebuilding FastFile. Best to do this in Windowed mode with dual screens (one for game, one for UltraEdit)