Mabel's is spectacular. Come with a small group of people, order one serving of meat per person, and grab a couple sides. This type of restaurant encourages sharing and trying a bit of everything.
In terms of the food itself, I don't think there has been a single thing that I haven't liked. Potatoes, brisket, beans, ribs, turkey are all great. I think I was a little disappointed with a few meats throughout the different times I have been, but usually a little bit of barbeque sauce and help along any dryness or over seasoned meat.
Note that the seating can mean that you are sharing a bench with strangers. This has worked out well for meeting some nice people and gone poorly for running into some drunks fresh out of W. 6th.