Reptarium are my enclosure of choice, and I have more enclosures than most here on the forums. Many of my reptariums are nearly a decade old now, some even older- dozens still in use after all that time.
Here are what I see as the pros and cons-
*Pros-
Inexpensive
lightweight- easy to store
indoor/outdoor
zipper doors are absolutely bug-proof - keeps bugs in or out depending on what you want (reason I started using reptariums in the first place- for some reason had fireflies crawling into my bearded dragon cages and killing bearded dragons, later I appreciated their roach proof factor, keeping feeder roaches in).
Heavy mesh provides a little tiny extra shelter/shade from the sun. It isn't going to make much of a big difference, but the cool part of the enclosures are probably a little more moderate as a result (I heard someone on the forums once claim the heavy mesh traps heat in when used in sunlight- don't you believe it- that is total nonsense in my experience.)
Outer cover is economical to replace if something happens.
*Some cons and what to do about them-
-zipper door- for some reason people are a bit skeptical of this great idea. Stories abound of zippers failing. Out of a hundred or so reptariums I have used over the years, I've only had a couple of zippers fail, and those were on new reptariums, not old ones. Manufacturing defect.
After a few years, the zippers will sometimes stick or bind a little - especially if you have been using them outdoors all summer like I do. The cure is very simple- run a little vaseline along the zipper and it will work super smooth and better than new in a few seconds time, and will last that way for many months before another vaseline treatment is needed again.
-The other thing people don't like is actually having to work the zippers. This one is a real mystery to me- I'd much rather have a bug proof door that I can easily open with one hand, and open any where along the door frame that I want and open it all the way or just enough to get my hand in or anything in between if I want than opening a door on a hinge and having he door open all along the frame- I guess this is more from a non-chameleon standpoint say with geckos or something that might skitter out the door. But I still consider it nice with the chameleons to just open a top corner for feeding instead of having a whole wall swing open.
-The "rickity" frame. That's more of a problem with the larger sizes (say 175 which is mostly what I use) than with the smaller. Personally, I only move my cages 2x per year (outdoors in the spring and indoors in the fall) and they are empty when moved, so it isn't as much of a problem. I keep the cages on rustic tables made of 2x4's and these tables outdoors look like ladders horizontally on legs - two rungs are spaced exactly right for placing a potted plant on. Cages are tied down to the tables so they don't blow over in our sometimes rather dramatically windy summer thunderstorms. zip-ties hold climbing vines to the frames. In this setup and indoors where they sit on tables made for misting system drainage, I find them plenty sturdy.
-Poorly manufactured frames. This has been a problem the past few years. When putting them together the first time, often the joints crack the pipes that go between because the joints are a little too large or the pipes a little too small, not sure which. This has become for me a super irritant- I put together a dozen or so 175s last summer, I think I only had 1 frame that didn't crack somewhere during assembly because the stinking joints and pipes didn't fit properly. The worst example cracked at 3 joints! A single cracked joint isn't a big deal- the cover actually keeps everything together and snug and firm even with a cracked joint. But more than that and it starts to become structurally weak. My solution last summer was to add a bottom (a wall panel made for restrooms- 100 water proof- available at lowes) zip tied to the frame which secured all the weak breaks and held them together. But only because I decided to use that cage for bearded dragons. I don't want bottoms in my chameleon cages and if I had purchased it and only had a chameleon I would have been in trouble.
-In recent years, it seem the covers also suffer sometimes from poor manufacturing. Again those I got last summer have poorly woven mesh covers in a couple of cases. Not a huge deal for chameleons, other lizards like bearded dragons that are kind of hard on them anyway would go through them much faster.
-Mesh is not cricket proof. Crickets will chew through the mesh eventually at the corners. I solved this by simply using a food dish and not offering many crickets at a time. And by using lots of roaches which do not chew through the mesh.
-Visibility- I recently was out in my lizard building and it was late in the evening and I didn't bother turning the room lights on as I only ran in quickly to fetch something. I stopped, stunned at the great visibility of the lizards when the room was dark and the enclosures were lighted. All these years and I never bothered turning out the room lights. Now, that's a favorite part of my day because I can actually view the lizards much better. Unfortunately Indoors or outdoors usually the lighting in the room is bright enough that it limits visibility into the reptariums. I find myself constantly unzipping doors to get a better look at the lizards inside. Which probably means what I am likely to observe clearly is only the lizard and not the lizard doing normal lizard behavior. I can see the behavior clearly or the lizard clearly- I have to take my pick. In fairness, although screen cages are better in this respect, I'd probably not be satisfied even there. Years ago before reptariums I made some screen enclosures on a wood frame with a plexiglass door- Indoors the door was placed for observation. Outdoors I simply oriented the cages so the doors were on the north side of the cage- clear visibility and still outdoor friendly. Those were my favorite, but weren't bug proof or rot proof.
-I forgot to mention another possibility with the framing. My original 175 reptariums that I've had for so long have frames that I built from scratch with 1" pvc piping. I needed a lot and was on a budget (50 reptariums), so I saved about 30% by simply buying the replacement covers (I think they were a little less than $30 for 175s at that time) and quickly making my own frames for them. It was very easy to do, but I had to order the corner joints from a plumbing supply- not something anyplace normally stocks. These homemade frames are many many times sturdier and stronger. I can put heavy rocks and sand in these reptariums and still stack them indoors- gives you an idea of their strength. Smaller reptariums it probably isn't worth the bother and probably can't be done cheaper than you can buy them on sale for as a kit. But for larger sizes it does save a lot of money and the result is a better stronger enclosure. For really big enclosures (5' long x 4' high x 30" wide) two 175 reptarium covers can have a side cut out and then be sewn together with fishing line and a custom pvc frame fitted and you have a nice and large enclosure for about $100.