So, I looked at the discussion - some excellent points by everyone, and thanks for you input! - and did some more reading and thinking.
I found some other info that might shine some light on the writers' intentions here:
Detect Snares and Pits is a first level Druid/Ranger spell that detects 'simple' traps, and specifies that it's useless for detecting anything other than a basic snare, deadfall, potentially collapsing wall etc. It
will detect magical traps, but only of the types mentioned above (the
Snare spell was mentioned specifically).
So I'm thinking that if a
first level spell
intended to detect traps and
only available to two classes allows detection only of a limited sort of mundane
or magical traps, a
zero level spell that is much more general and available to every casting class probably isn't supposed to detect whatever magical traps are in the area.
So, from this point forward the ruling is this:
- Rather than forcing the caster to specify each time he faces a different direction with his 'cone,' Detect Magic will be considered a '360' Sense. This is the only part of my ruling that directly goes against the RAW, but it cuts down on the most cumbersome aspect of the spell (especially in PbP) and on the opportunities for me to screw with you guys if I'm having a bad day ("You didn't specifically state you were facing North by Northwest, so the magic never showed up!")
- Detect Magic will not automatically detect magical traps - trap detecting is a 'specialty skill' of the Rogue class and one of their primary contributions to the party, so we're gonna let them shine in this area.
- Using Detect Magic will grant a +2 'favorable conditions' bonus to the caster's Perception check to detect magical traps.
This seems to me to strike the best balance between 'autodetect' and 'worthless for detecting,' and takes into account the fact that Perception checks for detecting magical traps are specified in the rules as written, while detecting them with Detect Magic is not.