Despite the negative reviews, I still gave this and Item # 73-4377 try. It does actually work well, as long as it is used with care. First of all, do not leave this tightened down on your sanke coupler while it is not being used, that wears out the rubber O-Ring quickly. Second, the rubber O-Rings wear out quickly in general. Thankfully, they are nothing more than a standard beer washer and you can replace them with Item # 40-1914A very easily. They are not glued in or anything, just pull it out and put in the new washer. As long as you replace the washer frequently it does a really good job! If you are going to leave it connected to a keg in your kegerator for months, I would recommend putting Teflon Tape on the thread as well.
I bought these, against the negative review. However, given I'm already into kegging, I had a few of the thicker orange rubber seals to put on them instead of the standard black. With that modification, the seal was tight and they worked like a charm! They are quality manufacturing, and the factory fault is only in the stock seal, which I could see myself was a problem.
The o-ring and poppet are poorly designed, resulting in CO2 leaks. I have ceased use of this product.