Remington core-locked has really proven itself to me too. If it aint broken don't fix it!
I must say though, the new Remington core-locked ultra looks pretty impresive too but I can't remember a time when the original has let me down.
When calling coyotes, more often than not they will circle on a target they are
coming into and approach from the downwind side. Presumably they do this in
order to align what they smell, with what they are hearing.
This means that you should always have your downwind side camouflaged and have
an open shooting lane. If the area is heavily covered the coyote could come in
take a look and be gone, with you none the wiser.