I'm in the UK but my phone is from Germany originally. I put the German JB ROM on my phone as soon as it was released, using Odin, since I received nothing OTA or via KIES. But after a few days with it, and despite thorough wiping, I found battery life to be very poor with WiFi enabled. I tried to get to the bottom of the problem but could not spot the reason for the drain. I posted on the XDA forums and I'm not alone in my disappointment.
Yesterday I wiped the phone and returned to ICS, again using Odin and full wipes with Philz kernel. A few minutes into setting the phone up I noticed the OTA update downloading automatically. I let it download, but I am not applying it yet. I don't see any point. There are some nice new features, but the screen tap sound is annoying and the battery life with WiFi on makes it a non starter for me
I remember the days when we were all screaming to get ICS and the first couple of ROMs for that were pretty iffy. It seems to me that history is repeating itself again. Personally I would not be in a rush to get JB right now.