Lightbulb [Q] Xperia S - KitKat roms daily use + More questions

Hi,
I want to know if the bugs in the kitkat builds are noticeable when using the Rom in daily use, like: sms, phone, camera whatsapp, light games, browsing the web

Are the roms an improvement in compare to the stock rom?
How is the battery life? (Can it go through 3 hours screen on time on one charge?)

Which one is the best? (Cm11, carbon, Pac)

Thanks