my take after a day of using it, original unroot image here:
1) the performance: much smoother now. no longer feeling that unlock lag i get from 4.0.4 (which irritates the hell out of me~

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2) Switching of apps: the animation is abit liked iOS feel.. and it is smooth..
3) Contact Sync: now i can add Facebook as one of the sync app.. but i still cant sync my contacts over.. G+ works perfect.. but not Facebook contacts. HaxSync seems liked having problems in 4.1
4) Font size: As usual the default normal size font is way too small for my liking..
5) Google Now: a bit on and off.. was at a BBQ last night.. pull out Google Plus.. it shows me the buses for me to reach home which was neat.. i didnt even tell it where I am staying.. maybe i got the words wrong.. think i am not pronouncing some standard words correctly.. this morning was a bit of a miss.. as it didnt show me any weather..
overall.. JB is good. Project Butter should have been a project that is built from the very beginning and not now. There are reasons why iOS is so smooth is because performance is built in within its core from the beginning. But still PB is good but hope it irons out the performance issue of the OS instead of demanding for more horsepower from the phone..