I camp in mine all the time, it's far cheaper and easier than anything else I've tried. Rooftop tents are insanely pricey and very involved to put up/take down. This builds up and packs out fast, and I store it in a closet when I'm not using it. As it's gotten older, those buttons break constantly so I'm always replacing them. Keep a bag handy.
Winter and any kind of 'weather': it's been so much better to be in the bed of my truck instead of on the ground. It gets a bit cold still though because there's no insulation. I've rigged up an electric heating pad to cut some of the winter chill on really cold nights since my body has terrible circulation at times.
Summer: completely horrible. It's too hot and humid inside so you're forced to open the corners and get airflow going, but then the bugs get in and sleeping is impossible. For the summer, bring a tent. Or buy that screen window thing for it. Maybe that would work
Security: I built a sleeping platform/drawer system not unlike the video below. I installed an aftermarket lock on the tailgate so that I can lock valuables inside and not have to worry as much. With a big enough crowbar it wouldn't matter, but I'm just keeping honest people honest with it. (
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I haven't altered the shell itself, or really needed to. The drawer is the only thing I've done, and it's worked well so far