Well... I went with JB when Verizon sent it to me a couple of days ago! I figured what the heck and rolled the dice... LoL... Just had a few apps that didn't work and my weather widget was nuked... Many are claiming Sticky Notes app was nuked and lost all data (in any widget they had)... Glad I use another app... Of all things, I lost a very simple and basic stopwatch app... I found an even better classic one... LoL... Dodged a bullet!
Oh... And yes... Replying to myself... LoL... Ooops!
EDIT: I wish they would tell you what you may lose linked right to the update screen... Then you can scramble to back stuff up. Again, no big deal and way less painful getting used to the new OS since it is a lot like ICS... Runs a lot smoother too!
Not sure if your phone manufacturer modifies it, but android's standard clock/alarm app has a stopwatch built in.