Yea, I've been doing some research on it too, and was initially interested in them b/c my TB is gaining weight (slowly). He's almost 16.2 hands and only 990 lbs (and is up almost 200 lbss) and as he continues to gain weight and muscle up his shape will change. But then, after I posted last night, I read that they're not good for horses with a prominant spine...which is def. My boy. I guess they're better for wider backed horses?
But I'm still interested in what others think of them, and what their experiences with them are.