After the initial install and a few hours of use, I have to say I'm extremely impressed. The build quality is excellent, much better than I even expected. The liner is extremely tough and durable. Once inflated, the walls are sturdy enough for me (195 lbs) to sit upon without deforming much at all. They are much more rigid than I anticipated them being. The bubbles are quite vigorous, and although there are only 4 of them, the massage jets are pretty powerful too. I'd say they're nearly as strong as my whirlpool bath tub.
Everything went together easily, and we were filling it up inside of an hour. The built-in inflation pump is a fantastic feature. The weakest point is the time it takes to heat up, but this was expected being only a 110 VAC system. We filled it with warm water and once it got to 101 degrees, it held that temperature just fine. I was surprised to find that the heater still works with either the bubbles or the jets running, but not both. From what I've read, previous Intex models shut off the heat with any water agitation running, leading to a pretty quick cool down.
We had 3 adults and a 10 year-old all in it simultaneously, and there was plenty of room. I bought a couple of the adjustable seats, and they work well. Once it got hot, I was happy to be able to sit a little higher up out of the water. I'll probably get 2 more at some point. But prior to that, sitting directly on the floor was quite comfortable. It's well padded.
The only disappointment was the inflatable pillows. They simply lay over the side and the slightest nudge knocks them off to the ground. But they're really unnecessary anyway. It's just as comfortable resting your head directly on the wall, if not more so.
Assuming everything holds up for 4-5 years, I think I'm going to be extremely satisfied with this purchase. After that, we'll probably look to get a real hot tub. But this will do nicely until then. I'll post more pictures and some videos of operation soon.