I have a Bob Marshall and a Black Forest (similar to Barefoot). They are great, but they are NOT one-size-fits-all. They also require a good pad to go with them. I use a
Skito pad and a
ThinLine pad. I'll be getting a
Skito Treeless Half pad for the black forest, as it's more affordable ;-).
You also get what you pay for. Buying a cheap treeless saddle is no better than a cheap treed saddle. You want to stick with good brand names like Ansur, Sensation, Barefoot, Black Forest, Startrekk, Freeform, TreeFree, Torsion, Bob Marshall, EZ-Fit Treeless saddles (new brand that looks REALLY cool!), Bandos, and Heather Moffet's Vogue and Fheonix saddles. Stay AWAY from Hilason, Maya, Sydney Saddleworks, Freemax, and anything else that retails or eBay's new for less than $500. These "copy cat" saddles copy the look of quality saddles, but they are often poorly made with internal structures that are not suitable for use.
I am a heavy weight rider (250 lbs), so I use a Skito pad and a ThinLine pad together; on of the simple
ThinLine Western pads. The extra pad under the Skito provides more weight distribution and is VERY non-slip. I feel quite secure in my saddle, even on green horses or "fun" trail rides. I use a 100% mohair roper cinch for added stability. For trail riding, I use an over-the-neck aussie/english style breastcollar (we have lots of hills!).
Here's my set up.
I swapped out the regular stirrups for padded, caged endurance stirrups. I have no problems keeping my leg under me for a "classical" position.
Some recent threads on treeless saddles:
http://www.horseforum.com/horse-tack-equipment/tell-me-about-bob-marshalls-46744
http://www.horseforum.com/horse-tack-equipment/opinions-treeless-saddles-43895/
http://www.horseforum.com/horse-tack-equipment/treeless-western-saddles-41600/