I've had my snuggy pod (grey, double) for 18 months now, and I so have had plenty of time for it to wear in and out, and have some thoughts on the design.
First of all, design issues aside, I LOVE my snuggy pod. I'm neurodivergent adult, and the cosy, dim calmness helps me feel safe and secure and provides a place of calm. This would have been such a revelation for me as a kid. I would not hesitate to buy another one when this one dies.
It's also fantastic for the winter as it makes things a good deal warmer. I just have a heated throw for when it's really cold, and I'm snug as a bug. Summertime, less so. It is, essentially, a tent. You're not going to get around that, but with the flaps all open it's not too terrible in the scheme of the overall terribleness of the heat of summer.
Now, the technical issues. Some of these are down to the size, I suspect a few problems won't exist in the single version, but may be worse in the King size.
I managed to get the mattress in the pod after some struggling. It's really a two person job. The harder part was getting the poles in their pockets securely, they're a very tight fit, and I'd argue far too tight, as the poles have forced their way out of the ends on two corners. I have fibromyalgia, and it really was not a fun job.
So, if you're disabled or lack strength, get someone to help and save yourself tears and frustration.
Because of the struggle to get the mattress in, once it's in, you can forget turning it. This isn't great, as you really do need to turn your mattress every couple of months. With two people and a big enough room, you might be able to rotate the whole thing (and live with the flaps at the wrong ends). This is where the entire thing could stand to not have a full base, and instead have something more akin to a fitted sheet bottom. The weight of the mattress would be plenty to keep it secure, but it would also make it easier to take it off and put it back on again when you want to turn the mattress, or give the snuggy pod itself a wash or an airing.
The frame itself isn't what I would call very secure. There's no frame on the base, so the 6 ends of the 3 arch poles rely on the fabric of the pod to keep things up and in place. It works to an extent, and the pod hasn't actually collapsed on me, put you might shove your bedding to one side, which makes it list sideways. Mine has actually slipped under the mattress and bowed out of shape a bit.
If you have a slat bed, like I do, then it's even less secure as the pole ends can sleep and go between the slats. My solution is I've got drinks caps on the corners which is better than nothing. The cheaper design improvement would be to have some chunky rubber feet that fit on the end of the poles on the outside. The better improvement would be to go the route of full tent, and have base poles along the bottom edges so the poles aren't going anywhere. Combine this with the fitted sheet base, and you've got a snuggy pod that's easy to construct on or off the bed, and then get lifted off easily when needed for changing bedding or turning the mattress.
The item bag is a great feature, but it hangs straight down. If you're on your own in a double bed, that's not too bad, but if you have a partner, then real estate of the mattress is lost, and someone is going to be clonked repeatedly by the thing. It could frankly do with being sewn properly into the side of the pod. It would also benefit for having one on each side.
My final issue, which isn't a flaw but would be nice to have, is the mess netting. The small panel at the top of each end doesn't actually do much for ventilation in the summer, and it would be better if the entire panel had the netting option, along with both side flaps. The reason? Mosquitoes. They love me, and I react badly to them. A mosquito net over the pod isn't the most practical solution as you're battling with getting out of it when you need to go to the bathroom, then getting back in, plus making it secure enough that the mozzies don't find a way in. Full mesh panels would make a huge difference, especially given summers are getting hotter and the mosquitos are running rampant.
All in all, fantastic idea, I recommend having one. But there are plenty of things that need addressing, and I hope that there's a Snuggy Pod V2.0 at some point that is more user-friendly.