If you are after a dev popular model, look elsewhere, like z1 or z2.
I know I am posting in the wrong forum for such a comment, and might have rocks thrown at me by devs of xda...but the stock rom is, despite bugs that affect all products, sony or not, this one is pretty decent. You don't need root to accomplish certain performance gains that were needed in phones of the past. I cannot understand why anyone would want a different Rom, and in the very limited and ordinary way I use the phone, I cannot see any features I would like to add on that Sony failed to provide. A humble personal opinion.
Take this with a huge fistfull of salt.. that's coming from a guy who thought so till about 2 months ago, where limitations of KK (not sony) forced me to root my device to gain rightful access to the sd card again. I am grateful to those devs who made this possible