Well, jelly bean is not the massive overhaul of android os we thought it was gona be. Its key features is increasing performance, and not the features.
The main thing that is new is SPEED. Most of the animations have been sped up and enhanced to make it more elegant but yet simple and fast. Also Google has incorporated "Project Butter", which obviously means to make it smooth as butter. Its all under the hood of the os and is not noticible in the UI. But it does speed things up.
The UI is changed not to much, the Notification drawer is improved. It doesnt just NOTIFY you anymore, it lets you know more than just the general thing, it gives you details.
And last but not least, Voice to Text, and Text to Voice, and Info to Voice. So its like google's version of siri, except its not called by a retarded name "siri" haha.
Yes, Finaly its here, and the LG Optimus One Group has started on making a port rom of it already and its only been out for a week or so. The project is named JB-One, in other words, jelly bean optimus one rom.
PS: dont try the beta of the rom i stated above, it bricks your phone a bit, just a semi brick with big consequences.