OK, so I ordered one, and it came in today (well over the weekend but I wasn't around).
So first impressions, it's really better than I expected. It has a nice feel to the charger/case. something of a rubberized feel. It is advertised for the GSM version, and they claimed that it would work for the LTE as well. I was a little concerned as the LTE is a thicker device. Lo and Behold, it does fit. I have the stock extended battery on my phone. With that on the phone and the back cover in place, the charger/case will still fit. It acts just a little like it is bowed (probably not a good description), but does snap in and fit just fine. If you have the smaller stock battery, then it does fit just a tad better.
I have no idea if the NFC works with this case on. I hope to try this out in the next couple days.
I played with it on the phone for about an hour. it didn't interfere with any real functions (playing Words with Friends and answering emails/texts). The only somewhat disagreeable part is that it does make it a little harder to hit the power button on the side and the volume on the opposite side.
I put it on a USB charger and it fully charged in about 2 hours. It has a power button on the bottom. hit it once while the phone is plugged in and it tells you by lighted color what percentage of battery is left on it. Hold for 3 to 5 seconds and it starts charging the phone. pretty cool. The charging of the phone is somewhat slow. Probably something akin to the way the car chargers work with these phones. I notice that the wall charger does charge the phone much faster than the charger/case or the car charger. When the phone is in the charger/case, and then plugged into the wall charger then it charges the phone first.
Looks wise, it does add a bit of heft to the phone. I think it still looks better than most of the humpback extended life batteries. It doesn't make the phone look any larger than if it was in an Otterbox. I have my wife's Samsung Galaxy S in the Otterbox next to the Nexus in the charger/case for comparison.
I will update this after a couple days of actual use to fill in a few more real world details.
Below are a few pictures...