I got my OTA of JB a few days ago. Most everything was working OK. Just a few minor glitches. For example no matter if I turned the phone off while on vibrate or full sound, when I restarted it the "droid" sound during boot was gone. I thought maybe they just completely did away with it. However, after an FDR it is back???
Today while using navigation LuLu (that's what I call her) would tell me something stupid after the fact...like after making a correct turn, which she told me to do, she would then tell me to continue for another 1/2 mile down the same road I just turned off of???? I would also get a random warning that the GPS signal was lost when in fact it was not???
However, after doing the FDR all is back to normal.
Right after the OTA I did a cache wipe and it may, or may not have done anything to help, but the FDR certainly did. YES it's a PITA to do an FDR but just go ahead and do it to make sure you are starting from as close to factory install as you can.
One other thing that I have noticed is that it takes a full day or two for the "buttery" feel to really settle in. I always turn my phone off at night. So after a couple of days I was getting that smooth buttery feel until I did the FDR and now it lags ever so slightly just as it did right after the OTA to JB. So my hope is that in a couple of days that buttery feel will be back. Why it would take so much time to get buttery I can only guess has to do with certain information being cached and or buffered somewhere as you use the phone more and more. So then, doing an FDR, or even a simple cache wipe after using the phone for a couple of days "may" in fact loose that cached/buffered information and make the phone slightly laggy again until it rebuilds the cache. This of course is pure speculation on my part based on 15 years of working with computers in an IT field and by deductive reasoning.