I have been on two trips with ECO--one in October, 2010 (Canyons of the Little Rockies) and a second in May, 2011 (Kayenta Passages). I am eager to go on more--especially Waterpocket Fold. They use horses to bring in gear so you only have to carry a daypack.
They lead the hikes, prepare all the meals, and share their knowledge of the area--old timers' stories, geology, archeology. You sleep in tents. The food is outstanding, the country spectacular. I would recommend ECO without reservation.