Extremely comfortable--definitely for the rider, and surely for the horse, as well.
Very adjustable--should fit virtually all people and horses.
I am used to riding primarily Western, but also English and bareback. But I feel like I am raised the most off the horse and have the least contact and "feel" with the Trekker.
I don't like the instability of the constantly-flexing treeless aspects. It makes me feel a bit insecure.
My personal preference is against dressage rigging, and the straps on mine are too wide to fit the typical Wintec girth, which I didn't know when I ordered it from the catalog.
Still, I would recommend the saddle if you like that sort of thing, as it's a very nice piece of equipment overall. I'd certainly suggest a few test rides first, though.