Which Is More Annoying?

[Kreekakon]

One good thing with poofers, if you use them periodically, and then place a real monster after those, you'll "trick" the player into thinking "oh, nother poofer", and when they'll walk into it... you get the idea.

I've experienced that feeling, and, IMHO, no, it's not good. It's more annoying to encounter that than being scared in my opinion.