I thought I had to step in here with my thoughts.
I have seen reviews and comments all over the web how great ICs is (and JB after ICS).
However I am sitting here scratching my head.
My experience is as follows.
Every update of android from google seems to serve to increase integration with cloud and remove privacy, so eg.
On GB can disable sync globally from the settings for all apps etc. and can also disable all background network activity on apps.
On ICS can still disable sync but can no longer disable background network activity.
On JB neither can be done until after the account is added to the phone and its already started syncing the global option is removed.
On GB can toggle animations, on JB this option is removed.
GB has a better launcher can add shortcuts directly, on JB I can only toggle background/wallpaper etc.
GB has a far superior dialer, ICS and JB I cannot only display phone numbers, I cannot remove pictures from display, I have less options to set per contact.
GB and ICS I can clear all notifications in one go, JB the clear all button is gone I habe to swipe each one away.
GB has a much better network unlock screen than both JB and ICS.
GB whilst in calls has a good button layout, in ICS and JB its regressed significantly.
GB and ICS can use wifi to detect location, on JB its now GPS only.
I also have observed JB is noticebly laggier than ICS to use, I did benchmarks which gave noticebly lower read speeds on the sdcard, I then decided to do a new quadrant benhcmark, my galaxy S2 on JB barely scores higher than my galaxy ace on GB

. On ICS the socres are mighty high but JB has some pretty bad performance regressions.
Phone runs very hot in JB Cool in ICS/GB.
The only advantage I see with ICS and especially JB is if you happen to need one of the few new features that they add, and they are very niche features. Also maybe if you need to use a ICS/JB only app eg. chrome is ICS+ only. I do see lots of people saying they better but they never really say why, simply saying "new features" is too vague because all I see is cut features not new ones.