I have used Kit Kat for a month now and have tested Retail and O2 versions and therefore there shouldn't be any problems with a wrong flash and in both versions i have experienced micro stuttering everywhere ranging from Notification bar to going through home screens, I haven't experienced this with jelly bean as it runs more stable. I haven't noticed a difference in Network connection and drops or anything as i never experienced in Kit Kat too. Like i said it runs a bit more stable so I would flash back Jelly bean and wait for 4.4.3 or 4.5 as it should be more Stable.