I found your site while searching for info, Preach. Read most of the map hacks articles. I especially liked sad story of info_notnull that thought it is a real shambler 8)
Great info, even though at least half of it is too advanced for me at the moment. Another thing that makes my life harder is editor behavior.
For example, I tried to recreate activated door from Dynamic Entity Spawning and it didn't work (as I described in 2nd question). Well technically it worked, but not in a way it supposed to - activator-button opened door and activated trigger ignored me.

Today I opened my test map and same setup works as it should without me changing anything.
Few other things happened.
All entities with info_notnull and InitTrigger classnames had their position and size reset. Remember I wrote about suspicious "-64 0 0" origin? Well, now it is correct since entity crawled to the center of the world over the night.

As for what I'm trying to accomplish, I had that weird idea of trigger_push that pushes player only while he is facing specific direction. Realized that movement and view direction both use 'angle'. Got confused and tried to make something simpler.

So far I can recreate trigger_push behavior and trigger_multiple with angle, but not mixed together.