I have an Assassin Smoker and you can use either lump or briquettes without any problem . The charcoal chute opens from 6" to 8" helping to eliminate bridging. I have used lump and briquettes with equal success. The lump does produce a lot less ash. I have mainly been using Kingsford blue because I have a gob of it that I want to use up.
The Assassin does a fantastic job and is available in both a standard and the larger 28. It comes with many features that other gravity smokers lack and it includes a BBQ Guru. For Labor Day I cooked 2 slabs of ribs, a small brisket flat and a 3lb boneless turkey breast, plus a big pan of beans all at the same time and they came out great. I encourage you to check it out if you are wanting a gravity smoker.
Here is a thread that includes a video of my first cook on my Assassin after seasoning it.
http://www.bbq-brethren.com/forum/sh...d.php?t=166449