I use it and it works very well. Pay close attention to the instructions (which you should do with any test) and you won't have a problem at all. I have never accidentally missed the endpoint. I've purposely gone by the end point to see what it would look like, and it's really distinct that you've done it.
It's easy to over-titrate, or go past the proper endpoint (it's salmon/orange colored), not brown (mix one drop of each reagent to see). I'm now using a 25 mL water sample (instead of the 10 mL per the instructions), each drop is 80 ppm, way easier to perform the test without overtitrating.