I own a Bob Marshall treeless and paid an extra $100 to leave off the horn. I never had any trouble at all with soreness for any of the horses I used it on, and I do a lot of trail miles annually. However, I found that the saddle didn't allow much for a rider's movement and pretty much prohibited a proper seat position. It's almost impossible to post in my saddle. I will add that it IS the right size for me, as I had to submit a bunch of measurements at the time the order was submitted. But it's a saddle that one can ride all day and never get sore!

Several years ago I bought a Chris Cox signature saddle when I'd signed up for a clinic and couldn't get a refund but could put the down payment towards goods. As much as I'd have liked to attend a week long clinic, I absolutely love my CC saddle. There was a delay in getting it as Chris didn't initially approve of the tree. He personally inspects each saddle before it's sent to the buyer. The quality of the saddle is beyond description, and the rider is able to attain a proper seat.

I have one of the original Bob Marshall Circle Y Treeless saddles, bought it new in Sept '96 and love it.  I've ridden it on at least 30 horses and the only one it didn't fit was a very overweight TW. 

I got it to fit my very wide mutton withered QH and rode in it in the mountains, etc  even sweating, no white hairs, and no bad behaviors.  It is vital that you use a pad with the correct support - Skitos with inserts.  I have 3 and alternate the.  You can remove the inserts to wash the pads. 

Mine is western, no horn which is what I prefer. 

My boy is short coupled, high hipped and has narrow withers.  Absolutely no treed saddle would fit him and he got sour on them.  I spend months researching treeless and finally settled on a FreeForm.  I was able to test a few but ended up with the Western Barrel LW model.  It's a great saddle for him, no pinching and sweat lines are perfect (nothing along his spine).  I use an Equipedic pad with proper shimming.

They take a lot of getting used to because they do move.  It definitely makes you a better, more balance rider.  Some of the "gadgets" I work with my system are a breast colar (up hills) and a no slip, waffled type, carpet pad to help it "stick".  They're cheap from Lowes or Home Depot and replaceable as they wear.

We trail ride both our horses and mules in Circle Y Flex Tree Saddles.  And, have for many thousands of miles and many years. Doc rides the old timer and I ride the Shawnee. These saddles mold to the mules back and then right to the next horses back. We ALWAYS use high quality Impact gel, ESP, or PC SMX pads.

Love them!