Who doesn't like MTM? That looks like WMTMW to me. Are those super secret spy laser weapon barrels in the center of the mid drivers where the dust caps should be? Pew, pew, pew! That's awesome.
I think the purists prefer that the center channel be the same make and model, and in the same orientation as the mains. My center channel is a horizontal MTM, though, and I have no complaints.