I could care less about bells and whistles.
EFFICENCY gains and optimizations. This includes LONGER battery life, more efficent (read faster) calls to external call outs (which is how they call out the ESS DSP). In otherwords, forgetting bells and whistels, there is a reason google themselves obsoleted 2.3.1 and that was because of instability issues. Hence why Google put out 2.3.3 within 1 month of 2.3.1 getting released which coincidetally, it is the goto Gingerbread OS. ICS and JB improve on the underlying system (efficencies and optimizations which are not to be confused with bells and whistles) as will every new iteration of Android that comes out. Be it better memory management, better multitasking, better power management, better hardware abstraction layer etc. Something gets improved.