I have a dozen ponys or so. They always work. Use galvanized pipe to avoid staining. Some folks say their clamps slip on galv-pipe but mine never have.
I do wish they had the larger foot like the Rocklers or the Bessys. If the clamp is as good I would be tempted. The trouble is if you shop around, you can find pony 3/4" for $100 a dozen. The Bessy's run a little more and I don't have any hands on opinion but assume they are good:
http://www.hartvilletool.com/product/12500