Very good thermal design.  Great aesthetics.  Ok, so this is what they gotta do (1) offer an ash screen for the top, (2) either (a) make the grate on the bottom removable to allow you to clean out ash beneath it or, better (b) make the bottom removable for the same purpose.  The bottom grate is permanently fastened to the inner walls, so you cannot get the ascot beneath it, as well, you cannot drain the rain out without turning the whole think upside down.  All that said, it is super slick.  A really great idea engineered and executed extremely well.  Make some practical improvements and it'll achieve its potential.