I rooted my HTC One X last night (I have the Tegra 3 model) so I could throw Jelly Bean on it, and so far I have really been loving it. The ROM I used is still missing some key functionality (the camera doesn't work at all, for instance, and there's no Google Now) and so I wouldn't recommend anyone install it on their only phone, but it's amazing to see how responsive the One X is with Jelly Bean on it. Pretty much everything is smoother and faster than on the Galaxy Nexus, and Jelly Bean looks fantastic on the One X's non-PenTile 720p display.
Battery life has been about the same as it was with ICS. The other interesting difference -- at least with this ROM -- is that now the app switcher button is now a menu button, and the way you bring up the app switcher is to hold down the home button for a couple of seconds (which is basically how it was pre-ICS).
Obviously once HTC rolls out their update it'll have Sense layered into it, but just the improvements that Jelly Bean brings in terms of responsiveness will make this a great step up. If I were HTC I'd be rushing to get an update out the door.
UPDATE 7/31 - Almost two weeks later I'm still really happy. Had one issue where I had to revert to stock and reroot to resolve -- which is par for the course with this stuff -- but since then I've been using the HTC One X w/JB as my daily driver with zero issues. The more I use it the more I like it.
