I've long used the Bissell Spot-Bot for the occasional stain from my cat.  The machine works great, but I've found the cost of the formula to be way too high.  Happily, I got to try out this pre-treatment, and am really glad I did.  Although it's intended to be used in conjunction with the regular formula, I decided to try it alone on a couple of mild stains (fresh ones).  Then I loaded the machine with plain water and walked away.  When I came back, the stains were completely gone - and at a fraction of the cost of using the in-machine formula.  I also like that using plain water to clean up the pre-treatment means I don't have to worry about any cleaning residue on the carpet.