Back during the Klinton era (ban) I purchased two kits from J&T. Back then there were not many , if any options you could get with a particular kit with the exception of upper choice being A2, or A4, and either an A2 stock, or fake collapsable, with no price difference no matter which options you chose. I think, IIRC, the price of the kit was $389.00 which included everything to make a complete firearm, with the exception of the stripped lower. So, for about $515.00 each, I had two complete AR's.
One of these was an A4 upper with a standard 20" 1/9 HBAR chrome moly chambered in .556, which I decieded to make into my varmit gun. I of course added optics, changed out the trigger to a decent 2 stage, and also started reloading. After I made these last two changes, this setup was very accurate. Good enough for 500 yard shots at PD's when necessary.
Throughout its life, the only problem I ever had was a broken extractor (sheared lip) at about 5000 rounds. I finally put so many rounds thru it, that I just wore out the barrel. It still functioned perfectly, but the accuracy was becoming marginal.
I found their customer service to be very good, with all questions answered. One of my pet peeves is a vendor being either slow to answer emails, or not answering them at all. That will get them removed permanently from my vendor list. I found J&T to be very prompt answering emails.
So, if I were buy another AR and I needed to make every penney count I personally wouldn't hesitate to purchase another one of their kits. Since I have never sold a firearm in my life, resale value means nothing to me. I personally am not too concerned about warranty either. I've only had one problem with any of my ARs, which I described above. And I think reloads voids the warranty with some manufacturers anyway.
I hope this info is beneficial to some here who might be considering going this route on a future AR. This is in no way meant as a blanket endorsement for J&T, just relating my experiences with them, and their products. I'm sure they can have problems just like any other manufacturer. Isn't it a great thing that those interested in the AR have such a wide and varied choice nowdays, not only with all the different manufacturers, but also all the options offered within each manufacturer?
ETA: I also own some Bushmaster, Oly, and RRA products, and have no complaints there either.