But I think Death-traps are good. Here's why:

There aren't enough to seriously hurt a characters con. If the same character walks into 6 deathtraps he loses 2 con. If he's intelligent no one is going to manage to loot his gear as a result.
6 deathtraps for one character is a hell of a lot to walk into. You have to be a slow learner for that.

Death traps add risk, which is necessary to justify rewards. The helpfile Josiah talks about mentions a "leap of faith". Where would the leap of faith be if you could tell that this wasn't a deathtrap and other deathtraps were deathtraps? It is pretty damn obvious if you ask me that this one is different if you look at room descriptions nearby.

Deathtraps that lead to other areas? I assume you mean things like the whirlpool? I don't see anything wrong with one whirlpool leading to an area while another you get stuck in. There is a command called "tell" that let's you ask people you know about whether a particular thing is dangerous.

Nastiest deathtrap I ever saw was a pond that if you drink from it kills you. But I still think that was really cool.

How any character can lose more than 2 con to deathtraps and find it a problem is beyond me. If they are an exploration character (which they'd need to be to find so many deathtraps) then they don't need con much. If they are not an exploration character, they won't encounter so many deathtraps.