I thought I'd share my experience of trials of various Jelly Bean ROMs on my Ascend P1.
I've been running JB b315 EMUIv1.5 for some time now. It's a beta ROM but runs quite well on the P1 with JB v4.1.1. This is a european release which has recently been updated to b336 EMUIv1.5. There is an issue with GPS logs filling memory on both of these ROMs that can easily be fixed by altering settings in file gpsconfig.xml. Root required for this.
There have been numerous JB v4.1.1 ROM releases for the Chinese market, b704 and b705 being most recent. I've tried both and I'd steer clear of b705, at least in the UK. I had many issues with network signal instability on the 3 network. b704 doesn't seem to have this problem. Again, both these ROMs exhibit the GPS log issue.
I've also tried the PACman ROM which is based on Cyanogen JB 4.2.2. It's a nice ROM but a couple of apps (youtube in particular) was in a very, very small font. Unreadable for my 50yr old eyes. As was the settings menu. Seemingly no option to increase to a reasonable text size for my eyes.
Now onto the choice I think I'll be staying with. JellyBeer 4.33 CM10.1 JB v4.2.2. It runs without fault and best of all is the battery life which way out-performs any other ROM I've tried.
All the ROMs I've tried are on the following Spanish forum for use on CWM/TWRP with google translate to help if you don't do Spanish... Thank you to all the developers for their hard work. http://www.htcmania....splay.php?f=889