Ok, so this thing is STURDY.
The trick to it is not over-tightening the bolts. If you manage to tighten it without breaking it? You're gonna have a pretty sturdy, very large cat tower.

I took one star off because it has a slight sour scent. I'm assuming that's the wood glue they used to attach the carpet and rope to everything.
It's nothing disgusting- and I bet it will air out over time, but the morning after assembly it definitely smelled of glue.

I have a 6 month old kitten who bounces off the walls. This has pretty much tamed her and she spends all her time bouncing off of this instead of running back and forth across the tops of everything (and everyone) else.

I have a 14+ year old ex-feral grizzled old alpha cat. I picked this specifically because of the ramps (his jumper isn't quite what it used to be), he won't go near it. The ramps are VERY steep. So steep that the 6month old actually fell and rolled down it the first few times she tried to hop down.
I think this problem would be solved by adding even just one more "rung" to the ramps to make them a bit longer and the angle a little more reasonable.. That's something we'll fix on our own at a later time.

Over all- it's a solid construction, EXTREMELY LARGE, and very pretty. I like finding it in black so it matches everything else.

To be noted-
The mouse that comes attached to it is some sort of plastic-y type furred creature. Our cat was constantly pulling the fur off and choking on it, so we had to remove it. This would be solved with a non-furred toy of some sort.. The rope is long enough to cut the crappy furry mouse off and tie something more suitable for your cat's enjoyment.

The larger box is collapsing on one corner, either the wood along the edge is broken or not measured right and not supported. Either way it is bound to topple if not fixed. So I requested a replacement - received one, no hassle. BUT the replacement has the SAME problem only worse. Definitely a flaw in design or packaging. So I'll be returning the replacement and cutting a 2x4 to brace the collapsing corner myself. Thus the loss of 2 stars. In terms of kitty-love, they give it 4.5. They took off a half star for the cheapo dangling mouse toy that they had dissected in minutes. Replaced with a bit of shoelace and they are good with that.
update:
We decided we didn't like how high the upper platform was, so I took it off, screwed the post onto the furry side and have it as a floor-level independent scratching post. The kitties like that a lot too. Also didn't care for the orientation of the larger (level one) box. We turned it around so the door is facing the platform - MUCH more play friendly. You either need to drill another hole for the support tube or leave the bottom sit "free". Now that I have a 2x4 supporting the corner I am OK with no drilled hole.

This is the worst made cat tree ever. It fell apart after not even 2 months of use! First, one section that my larger cat was sleeping on fell over. Then, within a few days, before I had a chance to see how I could fix it, all of the sections fell apart! The cat tree is literally in pieces now. See my photos, the camera doesn't lie!
This cat tree is so cheaply made because it is simply stapled to these plastic cylindrical pieces that are supposed to hold all the carpeted pieces together.
Do yourself a favor and pay $30 more (for about $130), and get yourself the better-made cat tree! This is a piece of junk. What really bothers me is that it is now too late to return it because I've had it now 2 months. They only have a 30-day return policy! I now have a cat tree that is all in pieces, and absolutely worthless. I had left my nice cat tree behind (which looked just like it, but was made WAY BETTER), because we moved to a new house. When I saw this new cat tree online, I thought, great, I am saving $30. But boy, was that a mistake.
This is a piece of crap, do not waste your money, do not buy it. You will regret it if you do and you'll write a review like mine.

Sadly this did not work for us. We bought it on May 11, 2015 (today is June 3, 2015) and my husband called me earlier today to tell me that the top two perches have finally snapped off. They started leaning within 24 hours after assembly. We had a cat house from Armarkat for 3 1/2 years. The only reason I decided to order a new one was b/c that one, which was still very sturdy, was showing other signs of wear - the carpet was lighter so you could easily see stains and the sisal had been torn off. I thought this one looked cool and loved the darker color, and the price tag. I think it was very poorly made. It was overall much lighter than the Armarkat cat house and clearly made using flimsy materials. I think next time I'll spend the extra $50. Sometimes you get what you pay for. This was one of those times.

First impression: This is a great size and design, but not stable enough. It's not going to hold together for long and the kitties are afraid to use it because it wobbles and sways.

1-week update: I substituted a larger plywood base for the provided fiberboard one. It is MUCH more steady now. The provided base is too small and flexible to support such a large structure.

6-month update: Two of the three top platforms are bracketed to the walls in the corner of the room. I removed the third one because it wasn't stable enough without a bracket, and no one has missed it. After I had had it a few weeks, I tightened all the screw connections. Since I set it up this way, I haven't thought about it twice. I highly recommend this product IF you are willing to bracket it to a wall (I used cheap shelf brackets from Home Depot and used a drill to attach them to the platforms and the wall). Ps, the fabric and sisal rope has held up extremely well IMO.

Pros:
1. Big. Real big.
2. Easy to set up.
3. Constructed fairly well.

Cons:
1. Parts are made of fiberboard. I stepped on one of the ladders by accident and snapped it in two.
2. Very unsteady. It will need to be bracketed to a wall in one or two places. The top platforms are especially unsteady.
3. Additional parts are necessary to make this sturdy enough for my active adult cats.

Construction materials that can be seen upon removing from box are:
1. fiberboard--platforms and tops/bottoms of boxes.
2. thin masonite--sides of boxes.
3. cardboard--supporting rods
4. plastic--ends of supporting rods
5. metal--brackets, screws, threads
6. plush fabric--stapled and glued to underlying materials
7. sisal rope--stapled to cardboard rods.