I got my e13ctron S4V all aluminum (non-hybrid) case about a week ago and finally found enough time to post a few pictures of the minimal signal issues. I
posted previously about the S4 not affecting my Verizon 4S signal significantly, but bought new S4V cases, so that the mute/vibrate switch cutouts were properly aligned.
Honestly, I believe the all aluminum cases work best for people who: 1) have AT&T AND live in a STRONG signal area or 2) have Verizon, who seems to have strong signal areas almost everywhere. I had the old e13ctron S4 (AT&T/GSM) case and used it in my area of southern California and areas overseas without deal-breaking signal loss or gps issues. I switched to Verizon with my iPhone 4S, as AT&T's signals actually got worse over the last two years to the point that I had to actually get an AT&T Microcell, just to make and receive calls while at home.
Here are a few photos of the iPhone completely naked (-94), then with only the back piece on (-90), then with the front piece on, but screws not installed (-92), then a shot with the full case with black screws fully installed (-95). The photos were taken within seconds to minutes of each other for comparative purposes.
The case works great for me, but again, your own experience will vary... most likely proportional to your physical location's signal strength and provider of choice!