AbdulAlhazred
Legend
If a creature is INVISIBLE (one of our states on page 277), it is only a minor action to determine what square it is in. One can make three arguments from here.
1) A Hidden creature is invisible (and silent), by definition. Thus, an opponent can use a minor action to try and pin down what square the creature is in. This does not necessarily negate the Hidden state, allow attacks without a penalty, or negate the hidden creature's CA.
2) A Hidden creature is invisible by definition. But one could argue that the minor action perception check falls under the "Enemy Activity" clause described under stealth, thus a minor action perception check blows the hidden creature's cover and it loses the Hidden state. This raises the question -- if one monster locates a hidden creature, does it remain hidden for everyone else?
3) A Hidden creature is invisible AND silent. Thus it does not fall under this category at all, and a minor action check can't be used.
Three is the correct answer because if a character is hidden, they are silent, which rules out the conditions for using a minor action to locate their square. I would rule a character which is both invisible and hidden cannot be percieved at all by sight or sound and would only grant an active perception check if the monster has some sense like tremorsense or extraordinary smell or something like that. Basically if you're a rogue with stealth, unless someone runs into you or something like that, you pretty much will stay hidden and you should be able to move around at 2 squares per turn even in 'plain sight' because you AREN'T in plain site, your invisible! Any new monsters coming into the room would get a passive check.
I agree the rules are scattered and could have used another edit, but the whole PHB is like that. There are places where you have to take it as it was meant or find errata. Stealth does work, it might even be said to produce fairly credible results. You can attack from stealth with CA (essentially an instant of surprise or just the blow lands before the enemy even sees you).
As an aside, and it might be obvious, but the greatest advantage of all of course is initiating combat while hidden. Now you get an entire surprise round, and if you can do something like the warlock shoot and shadow walk you can keep it up round after round, lol.