Joe started out in the fringe niche of UL. A lot of Cuben, and the really thin stuff. A lot of his early customers understood the limits of the gear and the need to be gentle with it. Over time he is moving to more robust materials -- maybe the market demands it or maybe too many problems/complaints from customers whose gear failed due to "abuse." I don't know.
His construction quality has improved over the years too. Sometimes I think he may be stretching himself thin with the breadth of his product line. Time will tell.
To be honest the construction is not quite at the level of Tarptent, MLD, SMD, ULA, GG, or EE - all companies I have purchased products from and have been in business a lot longer than Joe, except EE; but Tim concentrates on just one product. Then there is the upper echelon of quality such as Nunatak, WM, and McHale. These 3 I have experience with too. But Joe's products are completely acceptable quality-wise, given the nature of minimalist products.
I think another factor that is good for Joe is that are many people, like me, who can afford multiples of gear items that allows them to be very selective in picking gear items for specific trips.
If I could only keep one of each item I own I would choose my McHale Full Dyneema LBP 36, MLD Silnylon Trailstar, and WM Ultralight. Meaning my base weight would move from around 5 lbs on a lot of trips to around 8 or 10 on every trip. The McHale is my favorite pack. The MLD and WM aren't necessarily my favorites but they are robust, well made and can be used on almost all trips I take.
As my zPacks stuff wears out, I probably won't replace it as I am leaning towards stuff that lasts and can take abuse - items I already own. The one zPacks item I would re-purchase without hesitation is the poncho/groundsheet. I am not unhappy with any of Joe's products, but I do hike a lot and they just aren't going to last years and years for me.
Joe has his niche and does it well. I have nothing but good things to say about him.
Of course he probably doesn't like some of the criticism in this thread, but that comes with the territory. zPacks gear isn't for everyone, just as a McHale isn't either.
At the end of the day, what matters is that we spend as much time as possible in the wilderness. Whether I am using an old piece of gear or something leading edge it really doesn't matter that much; as long as I am safe, warm, dry, and walking.