On the other hand, the building returns to the original place every 2nd turn, and then you just put another building next to it, and - suddenly you have reach to another space as well! (Possibly well, especially with 2 visioned buildings.)
And used for creatures - your enemy can use it to send his creatures to your base too, and there's no way to prevent him from doing that (unless you put there your creature, which'd be out of fight for next turn.. and if he starts 1st the turn after he gets to you anyway.)
So.. I considering all this, I don't think it's that strong..
(Of course goes well with Loxlorn!)