Andor
First Post
Actually 30' ahead in a dark area. Ahead of itself, mind you, as it wanders around the dungeon on your behalf. You the caster can be sitting outside having a smoke and making a map of what it sees, complete with monster notes, as long as your concentration isn't interrupted. The spell write-up says the eye is created within range (30') of you but goes on to say "There is no limit to how far away from you the eye can move [on this plane]", and that's where it breaks.
Example: Wave Echo Cave (Lost Mine of Phandelver) - you could with one 4th-level spell and an hour's free time map just about the whole thing before ever setting foot in the place, and know what monsters and enemies to expect, and where. Sure there's a few doors your eye can't get through, but you know where they are and how to approach them.
Too good for one risk-free spell.
Lanefan
Or I could cast a 1st level charm person and have my new buddy take a break from his guard duties to tell me what's in the place he guards. He's been past the doors too. Maybe. Plus it's even better in town for your problem children players. I fail to see the horror in the arcane eye.
If you don't want your players to cast it then just make sure the first thing they see with it is a medusa. Or Jabba the Hut in the shower. Or an Otyguh on a bidet. The mind scarring possibilities are endless.