Beats a tent. But a tent is cheaper to replace if the canvas takes a tear.
Water is their worst enemy--that's true for any RV, or house for the matter. Check the corners of the box, the four corners of the floor underneath, as that seems to be the area first hit by water leaks. Check the caulking. Make sure they didn't use a silicon caulk to fix, as it tends to dry out and turn rock hard.
I have a 12' pup, I'm in decent shape, and I'd say it's maybe 15 minutes to get it set up. Half of that would be just getting it level. No slide out on the side; it's basically an overgrown version of the venerable 8' pup. Usually bigger is heavier, but mine is an older unit, so it's actually on the light side--they've packed on the pounds as the years have gone by. We like the layout, and while you'd be tempted to think 12' is huge for 4 people, try hanging out in a pup on a rainy day. Speaking of rain, one of my joys in life is sitting in the camper and listening to the rain (well at least when it is not pouring).
One issue is packing. It's annoying to open the camper to pack up for a trip. On mine I can't even get to the fridge without cracking the top. With my overgrown station wagon though much of the travel gear goes into it instead. So some stuff goes into the camper (utensils, stuff that can stay in it) but much of the last minute stuff goes into the truck, at least for travel. I like to think it keeps the weight off the trailer tires, maybe it will let them last longer. Make sure you have some outside compartment doors (my 8' lacked those, chock blocks had to be stored in the tow vehicle). The storage trunk on the front can be great, but many of them are blocked off to the world when the bunk is pulled out, and they can be a source of leaks too.
I don't use the water tank; I just buy a few gallons of water at a grocery store, and refill at the campsite. That way I can skip on the winterizing stuff. Call me lazy.
I tarp mine in the winter, mostly to make snow removal easier, but also just in case of leaks.
Popups have like zero insulation. Their ac won't keep up on a hot day if it's located in the sun--some will drape additional layers of insulation over the bunks. Likewise, I don't think you're going to stay real warm below freezing (and many worry about cracking the canvas in sub-freezing weather also). I've toyed with getting a portable ac unit as I don't trust the roof on mine, but word is the ac unit on the roof is the way to go--all other options aren't that great. That is the one thing I wish I had, as our family doesn't do heat&humidity real well. Otherwise, I do have a furnace, a tiny fridge and a small sink, along with decent counterspace.
Lift systems can be costly to repair--or cheap. My first pup wouldn't open so I bought it on the cheap. I lucked out and it was a Goshen system, which uses basically a boat winch. $20 to replace the entire cable and away we went. The current pup is an L&W (?) and a bit more complex; others have the cable systems buried inside the camper--good luck with repairs. Thankfully repairs aren't that common, and usually the systems are mechanically simple. One thing to watch out for is ABS roofs. I'd avoid them, on the basis of doing some reading; but some aren't scared of them. Do your research if you think about getting one with an ABS roof.
Friends of ours just got a popup, as they figured it'd make for cheap(er) family vacations. Why get a hotel when you can stay at a park? I think you have to be careful here: if it's just for a few nights, the drop in mpg, the purchase cost of the pup and incidentals might not work in your favor, as compared to a couple nights in a hotel. YMMV, but if it's being done under the though of "it's gotta be cheaper!" then do out the math. Our friends did have to buy airbags for their minivan and a brake controller; cheap money but it seems camping keeps running into those little added costs... Myself, I had high hopes of getting a travel trailer so my tow vehicle is way oversized--but on the same token, it pulls my trailer with ease, which leads to a very peaceful, relaxing time. Zero worries about loading. Which is how I wanted it in the first place.
Good luck.