Geez . . . Paul, Ken and Mike in a discussion about anything is
a priori going to result in a metric crap ton of "life experience." (Remember, guys, you are only young once, but you can stay immature indefinitely.

)
My take on the Tern windows has four parts. (I get to hijack my own thread; there's more on the topic elsewhere.) First, all credit to the company for making them available. It was a long time ago, but I and others thought about trying to get non-Seitz windows imported--I actually used a window that I bought from an inmate who ponied up to get the minimum order to resell--but the Arctic Terns became available at a great time given the huge increase in both commercial and personal camper builds and Tern Overland made it work. So good on them.
Second, I figure the windows must appeal to most builders because they are
everywhere. Admitedly, some of this is from a lack of options. If anyone knows a UK/Euro supplier eager to ship to the US, it'd be a public service to let everyone know, but I consider importation under current conditions impractical. You can, of course, get reasonably-priced acrylic windows off Alibaba or Amazon or from some other sources, but the support and expertise Tern Overland supplies is worth quite a bit. (I've never had the Outbound windows, but they look to be at a different level. Their price list is on the web, so you can calculate whether the improvement is worth the cost increase. And there are other manufactures of glass windows with even bigger prices.)
However, and third, I don't think the Tern windows are any gift to clever engineering. Mine work, and I don't think of them as flimsy. They're nowhere near as flimsy as their Seitz equivalents, for example. In fact, I think they definitely weigh more than they need to. And while I find the up/down and "clasp" mechanisms to be adequate (and better than the rear Seitz window's), they have some weirdities. The little clerestory windows at the top side of the XV-JP have FIVE turn latches, the same as the three-times-larger main window below. And there are only a couple of angles you can open those windows to, and it's the same limited number on the big window, which could fruitfully have many more detents. (I'm close to disabling the big window "catch points" and using a clamp on the strut to allow infinite adjustment.) Still, while they have none of the "special" feel you get out windows costing significantly more, mine don't strike me as flimsy or cheesy.
HOWEVER, and fourth, in my personal situation with the XV-JP, my dislike of the blind/screen cassette is unbounded. The whole cassette is huge and the hinged metal covers for the rollers are more huge-er. The situation is bad on the main window, where the cassette adds significant width and height to the effective dimension of the window and the bottom roller cover sticking out costs a couple of inches of useful counter depth while the top cover makes it impossible to mount the handy over-window tray Paul crafted. I currently have the cassette on, but have also spent time with it off and a nice roller shade replacing it. There are pros and cons to each approach.
It's worse/absurd on the clerestory windows. The depth of the roller covers--no smaller than on the big window--makes the cassette foul the roof angle at both the top and bottom and I cannot install them at all. I've had to make separate magnetic-mounted screens and blackout curtains. You'd be right to think that the measurements for the depth were available, so I should have known the cassettes wouldn't fit. I did know and needed those windows regardless of the cassette being a waste. That said, though, I'm allowed to be grumpy because it didn't have to be that way. The roller covers seem enormous for the space required to house all of about 9 inches of screen/fabric. It's also the case that the cassette for the Seitz windows would have fit; their integrated rollers do not protrude beyond the frame. Overall, the Tern cassette seems about two times thicker and heavier and pretty freakin' clunky.
The whinging about the cassette is admitedly mostly a result of my specific situation, but you should be aware of the problem. While it often won't matter (and some will inset them into a wall so you don't even see the roller covers), there are many instances where the bottom roller cover could be in the way of your sink faucet, cooktop, or the back of your head when you sit. Check carefully. But beyond that, I think the Tern windows are a pretty useful product, even if they're devoid of any of the elegance Paul'd prefer to have in his builds.