I've got this smoker and it's an absolute BEAST! I only received it last monday so haven't got doing any cooks on it yet, but I have seasoned it. I can confirm that the metal is impressively thick. 3.5mm I measured it at. This thing packs some weight! You can tell the quality of the steel just by the weight of the doors when you lift them up.
I have done a few mods to it so far - I used high temp silicone to seal where the firebox joins the side of the cooking chamber, I put smoke seal strip around the cooking chamber door and the firebox door. Due to the weight of this smoker it was very difficult to manoeuver using the handle that's on the firebox, also I didn't like the fact that you have to lift it by the firebox, so I changed the wheels over to the firebox side and now use the side table as a handle to move it around. This has made a huge difference because the weight of the firebox actually works in your favour this way and I can now move it around easily.
There are a serious amount of grates that come with this! It's pretty much a 3 in 1. You can use it as a smoker, you can use the firebox as a small bbq, or use the main cooking chamber as a large bbq. All the grates are there to do these things.
The thermometer that comes with it is poor, but aren't they all. I use digital thermometers anyway and I'm going to drill a hole in the side to fit a steel gland to put my probes through.
I've attached a few photos of mine, these were taken before I switched the wheels to the firebox side. I got a mate to make me the heavy duty charcoal basket.