Plane Sailing
Astral Admin - Mwahahaha!
I find it frustratingly vague. It says you can study the auras to gain clues into the nature of the magic, but it gives absolutely no information about what counts as "study", what the DCs should be or what kind of information you gain. It also says that it can't detect magic that is designed to be hidden, but what is that? Does that mean every illusion is immune to detection? What about polymorph type effects, alarm spells, or other wards? Considering how rules-lite this spell is, I doubt I can expect to find any help in the other spells' descriptions about whether or not they're "designed to be hidden."
This is not the kind of stuff that I want to just make up when I DM! This isn't DM "empowerment," this is forcing the DM to make up rules when he really shouldn't have to. I'm saying this as someone who often DM's.
For me it is empoweringly vague. It is exactly what I want to see. It allows me as a DM to apply common sense without opening the doors to rules lawyering and the vulnerability to special cases which are later added.
I love it!