For me the IR gives me the ability to sit in controlled airspace at FL100 above all the zones, areas, changes of QNH that make a long VFR flight quite stressful on occasions, especially flying low level VFR in France. (Incidentally you can use the airways in France as a PPL as long as you fly at quadrantal levels plus 500 ft) which is something you can't do in Blighty.
It also allows me to do approaches in IMC outside England. For me that is it's utility. IFR in Controlled Airspace is simpler, safer and considerably less stressful than the alternative. (Ice and Thunderstorms permitting of course).
In short it gives me greater utility.