That would depend upon what detergent one is using.Tide, Persil and many other tip shelf commercial and domestic laundry detergents clean, whiten, and in some cases disenfect at temps of 40C and even 30C.
This summer because of the insanse electric rates, have been doing much of my whites at 100F or 120F instead of 140F or 160F, using either Tide with Bleach, Persil or a commerical laundry detergent from Germany by Krussler (sp?), and have noticed no difference in cleaning performance. For that matter Tide Coldwater out cleans most other detergents by a mile, even in cold water.
Think as energy prices rise, and consumers either by choice or laws are forced to lower their energy use, we will see more laundry products that perform very well in warm to cool water. Commercial laundries, where every penny counts, have had access to these types of detergents, which helps their bottom line as it lowers energy costs/allows them to stay competitive.
As one who does quite abit of ironing, warm wather washes make my ironing day easier as hot water causes more wrinkles, creases. All dress shirts for instance, are done using my Miele's PP cycle at 100F. They come out perfectly clean and almost wrinkle free. After line drying abit, a quick ironing is all that is required.
Finally lower wash temps, speeds cycle time as one does not have to wait for cold water to reach hot or boiling temps.