I have a Pitts & Spitts Horizontal/vertical combo smoker with an offset wood box.
Horizontal cooking surface is 2x4 with a second shelf that is 1x4 (feet). Vertical has two 1.5x1.5 foot shelves. (Propane can is for quickly starting charcoal or wood.)
I've had this for over 12 years and have been generally very happy with it. P&S are located in Houston, Tx.
They use a minimum of 1/8 inch rolled steel for all their pits, it is very heavy duty. Mine has been used a bunch, and traveled around the world with me and shows no signs of metal fatigue even around the fire box. Their air inlet is a plate on a bit bolt, you can screw it in closer or open it up - infinite positions and it works very nicely in controlling the temp. The exhaust is on the top of the vertical section and has a good rain hat. I've gotten good, stable temps in 110+ hot days in Tucson and in -5 and snowing in Norway very easily.
I've cooked a truck load or two of briskets, ribs, pulled pork, etc. on this over the years - they come out great. I had never done real BBQ before I got this - and my first ribs came out wonderful something about the right tool making the job easier...
The only downsides:
1. The right side of the horizontal section (right next to the fire box) can get 25-50 degrees hotter than the left end - so if you are filling it up, you need to rotate the food.
2. it is fully manual - so you have to keep feeding it wood/coals. It usually takes me about 45 minutes to get to a stable 225 temperature after starting it up, and I need to "feed" it every 2-3 hours or so.
3. I find that in really hot weather (which we have a bunch of in Tucson), I don't use it as much as keeping a good set of coals going just makes me that much hotter - I use my Pellet smoker all the time in the summer and the P&S more in the winter now.