Been using it for over a year now and my towels come out much better than when I was using Free and Clear detergent and a vinegar rinse. Much the same situation as Dellinger--1.5 oz per load with hot water, but I no longer do the vinegar rinse--towels come out very soft and fluffy. I don't see how the other more expensive products on the market could do any better.
A note on Towel Kleen: I store mine in my garage that is insulated but unheated--never gets below 42 degrees--in the winter the Towel Kleen turns to a milky green, then back to clear green when in warms up, but does not affect performance.