I just purchased a genuine Metal Slate color Slim Armor from my local store.
I insalled the Qi charging PCB receiver, and put the phone into the Slim Armor, works wonderfully.
The Qi Chargers I have used are a Japanese NTT Docomo Qi charger that came with my Fujitsu smartphone last year (which supported the Okudake Juuden), a generic white color USB based Qi Charger off eBay.
Both chargers works wonderfully, but the Docomo Qi charger has slight fast charging rates... I am using the original 2 amp charger that came in the S4 box. The Docomo Qi Charger can output 1-1.5 amps. My PCB receiver can receive around 0.7-0.8 amp (measured)
I can charge around 16-22% in an hour. When the battery hits 80%, it charges around 8-12% an hour... It also supports trinkle charge when it reaches almost full charge.
I can fully charge my brand new S4 with a brand new battery at full capacity in around 4-5 hours of time. If your battery has already worn down from discharging and recharging cycles, you can probably finish charging faster.
With the PCB Qi receiver, my NFC works very good even within the Slim Armor case..
I also tried to use the Qi receiver with the Otterbox Commuter, but has shaky connection with the charger. Even when the resonance frequencies pairs up between the receiver and transmitter, it emits a ever so slight coil frequency buzz. This is probably due to the fact that the distance between the 2 coils are at a minimal contact distance. If it charges, the charging rate is very slow, and sometimes when using the phone with light load like music listening with screen on, the battery recharging input is too low to keep up with the battery discharging rate, so I still lose battery percentage although I am plugged into the wall.
Hope this helps.
Rogers Samsung Galaxy S4 Black
Rogers Samsung Galaxy S3 White
Fujitsu F-02E (White)
Fujitsu F-06E (White)
Softbank X01HT/HTC TyTN (Hermes 200) - WM6.0
Samsung Wave S8500 (The Wolfson DAC + my Fiio E6 amp)
Rogers Samsung Galaxy S2 LTE
Rogers Samsung Captivate
Rogers Samsung Galaxy S3 LTE 16GB Blue
NTT Docomo Sharp SH-06D