just wanna share my experience based on one day usage:
1) face unlock is fine, as long as the environment is bright. and the angle of the face must be the same as when i first setup the face unlock. if these 2 elements are fulfilled, the phone will unlock in a second! but 99% of the time i have to use the pattern unlock.
2) battery usage is awesome. just 28% decrease in 9 hours and 31 mins. and that with moderate usage and live wallpaper on! sorry couldnt test it hard enough coz it's a loan phone and i dont want to cause havoc in the office that will lead to every single android fans in the office play and test the phone.
3) voice recognition works well either in english or in malay, as long as i specify which language i wanna use and not set it to auto. and the internet connection must be fast and stable.
4) new market works amazingly fast on this ics unlike my note and sgs2, where it's loading time is a bit slow.
5) picture quality is poor. it half the quality of sgs2 and notes and even poorer than my htc sensation.
6) somehow i wasnt able to play 720p and 1080p mp4 videos.. these video have no problem playing on sgs2, notes and sensation.
7) no usb mount storage is troublesome, at least for my usage. it can only use mtp like galaxy tab 10.1.
8) somehow usb mhl adapter for my sgs2 / note does not work for galaxy nexus.
9) whatsapp sometimes lose contacts. i have to keep on refresh the contact. i never experience this in my other androids, so maybe it just a compatibility issue between whatsapp and ics