I also agree- the acoustics get worse, but the difference is quite minor, IMHO. Slightly less "thock." It "feels" more solid, but that could be psychological.
The two halves of the case are held together by four screws. On mine, the screw thread on one of the holes wasn't deep enough for the provided screws, which meant that I had to trim about 3mm off the tip of one of the provided screws with a dremel to make it fit properly. Ugh. (That's the sound of me being annoyed)
Build quality is quite nice, other than that one problem I mentioned. It feels very solid, and looks classy. The anodising is also well done. The aluminum in the case is actually connected to the USB cable's shield (I checked continuity with a multimeter) which indicates some thought above "let's make it look shiny so we can sell it to people" was put into its design. I appreciate that.
I had no problems with the daughterboard on my unit, but I have heard that some people got defective ones. Hopefully they fixed the issue in one the ones they are selling now.
I'm unaware of any other metal Realforce TKL cases being sold right now.