Passive perception - all secrets revealed?

[Mistwell]

Any Elf Archer-Ranger(Rogue Multiclass) is equal/better at perception and thievery than the party rogue... He's got 2 stats he needs for anything he does: Dex and Wis, which just happen to get a racial boost and add to any rogue skill. Oh, he does have another racial bonus to perception. Take alertness at lvl2 (lvl1 is the multiclass feat) to increase the fun.

Of course he cannot use his primary rogue ability (sneak attack) unless he chooses woefully suboptimal weapons...

 

[Kordeth]

My question is how does passive perception really work in the 4th ed. Are all spear trap floor mechanisms instantly seen by the high perception party member? Are all secret doors now instantly revealed? Or does the DM give a hint about them (which is one step away from actually telling players).

Passive Perception is merely the assumption that all adventurers are always taking 10 on a Perception check. If the character would be able to see it by rolling a Preception check and rolling a 10, he sees it automatically with Passive Perception.