Picked up my Black Mist 16Gb GS4 today. Swapped out my GN2, somewhat reluctantly. But I'm liking the form factor of the GS4 better.
Edit: I had initial concerns about battery life, but phonedog.com's review seemed to indicate no issues in that regard.
My battery had about a 60% charge when I picked it up today. After 10 hours of sporadic use doing setup, phone calls, texting, etc. I still have 30% left. I'm pretty amazed if that turns out to be true going forward. In all fairness, I've been in wifi most of the time... probably 65-70% of the time.
Edit 2 on 2013.04.30: after 18 hours in service today (light service, a few texts, calls, and some light browsing and playing), I still have 71% remaining. I am impressed.
Edit 3: 2013.05.01: I left it on overnight, not plugged into the charger (my norm). When I checked it this morning the battery was down to 68%. I plugged it in to charge and it took right at one hour to bring it up to 100% charge.