I ended up with a HUGE setback trying to get cute with vertexes. I was making door frames and window frames, and almost all of them errored out.
To top it off, something happened to my file, corrupting it so that it had a "too long or open string" in it that took me about an hour to figure out how to fix it.
Finally, every time I go to playtest it, instead of loading up L4D2 like it should, it loads up normal L4D2 without letting me playtest my map or just plain crashes to desktop.
Plus, I gotta resize a bunch of the floors of the tetris blocks, since it keeps telling me "Too many light faces on surface XXXX XXXX XXXX" which means that the floor is getting too many separate light sources.
All in all, instead of a good day of finishing up the 1st floor and getting a good start on the second floor, I've ended up with a wasted day, lost all my work that I did today, and now can't test it for the lights and everything.