I love my Lang 60, and when I replace it, it will be with an 84 Deluxe with chargriller. The pros are that it is a great smoker which wins a lot of comps, and is extremely even cooking with the reverse flow design. I believe that this is the best smoker for the price. The cons are probably the level of refinement. When you compare the Langs to a Klose or Jamie Greer pit, they look a little rough around the edges. However, I use mine, and am not afraid to get it dirty! Also, Ben Lang does not make pits as large as some of the other manufacturers, and the reverse flow only has an advantage to a certain size smoker. But as you can tell by my pics, the 60 is a pretty big smoker!
Edit: The referse flow baffle eliminates the hot spot (you will always have warmer and cooler spots), and makes this cooker extremely even cooking. If you look at my pics, you can see that you can use the entire smoke box, which is the advantage to this style cooker. You wouldn't dare put food that close to the fire box in a comparably sized traditional offset! ;)