UM is great, been using it for years. It does scum up if you mix it with very hot water, so mix it with warm to hot water. As I understand it, if it is used above the reccommended temp the enzyme is killed off, and so loses the effect of that additive. However I use much hotter than that through my TM and always get brilliant results. Since I used it my clients tell me that the carpets stay clean longer than ever before. That may not seem a good point as far as jobs are concerned but, the refferals definatly go up, so that makes up for the longer gaps between repeat work.
Dave.