I got a 20" standard JT kit. It has been 100% reliable except with a Thermold magazine that has a bad cracked feed lip. even then it feeds perfectly if you jam the magazine in REALLY hard to make it seat fully.
So far I am completely satisfied that my kit gun is as good as anyone elses I have shot with.
One complaint. The barrel nut worked loose. I have tightened this already, but for some reason it still grouped good even when the nut was a little loose. It still shoots as good as new now.