UPDATE: received. so, yeah, got it, it looks sleek when installed on the phone. I haven't seen the other battery covers yet, but the clips on the mugen seem to be the same cheap plastic like the other covers. i could actually tell looking at the clips on one side of my cover that they would likely break, as the poured molding for the clips actually extend/have a lip out side the cover (only one side/set of clips had this issue). broke one on first removal.
also, if you request black, the cover will be the same charcoal grey that your factory metal cover is. as i said, it looks very nice installed, but just as likely to break as the cheap covers (which is why they're available separately).
also note; the microphone hole for the camera is covered by the cover. i do have a dremel tool, so I can remedy this if need be. i've never used the camera or the front mic to date tho, so i probably won't.
i'll be ordering some batteries in the near future, so i'll take many pics and see about providing dimensions for the covers, so maybe some manufacturer can come up with a case cover for the phones w/ extended batteries like so many other phones/htc devices have.