While I find this situation neither painful nor obvious, I agree that CS and Grabuto have it right here.
An update is probably in order though, to make the wording more clear if that is the intent.
...and slowly, as the comments accumulate, the balance shifts. What was obviously so to some is now equally obviously
not so to others. This is why I raised the question in the first place.
Here's what I think: RAI, the feat is melee only, but the writer made the mistake of thinking that the final clause made it clear, while in fact, the lack of the adjective "adjacent" before "enemies" made it not only ambiguous but also departed from the standard style of most of the newer feats, which tend overall to be unambiguous to the point of redundancy. RAW, the feat is unrestricted, because a creature with no one adjacent still meets the criterion, regardless of what CS, Grabuto or shmoo2 say.
I will note that with the more liberal interpretation, it makes the Thief's Ambush Trick completely pointless so long as you don't mind spending a feat to get Cunning Stalker. In every case where Ambush Trick could be used to get CA, it is granted automatically via Cunning Stalker (no one adjacent at all) or by using Tactical Trick (one or more creatures are adjacent to the enemy, but those creatures are allies of the PC). Because Tactical Trick is superior in every other way to Ambush Trick (no 5 square limitation, and superior in its movement clause), Ambush Trick becomes a pure loser -- a
Red power in CharOp terms.
So we can probably expect a revision of the feat, either to clarify the ambiguity or to nerf it because it is otherwise just too good.