I admit, I can't imagine it working well in big games, or rather, games too full of people, where there's no chance to get to the "usefulness spot" without dying (even though, note that if you can't prevent dying on your way, it either means such spots aren't that necessary for kills, or someone has actually reached one of them). By "useless powerups" I didn't mean Ice, EB and Pepper Spray as you probably understood, but one of the other weapons which is just hard to use in the level, due to its layout. Take a level where Bouncers are the best type of ammo, and place them without a PU and RFs with a PU in it - a player gets a choice between a heavy weapon and a light one. Almost like in a serious FPS game. And about your example, I was never too much into PU in the wall idea, however again, in small games it shouldn't make a harm. Spawn time should be lower than normally though.

You two also made me realize I'm not thinking about fun while level-making. Not that I'm going to change that. I feel more like an artist than an entertainment provider and I won't resign of it, even if it results in my levels not being fun to play in. I heard MULCH is fun to play in too, and imo it's not a good example of the art of level design.