Rob, this is not first hand info, but most of the feedback I have seen regarding the round bar posts is that they put the tool to far away from the work. If, I were gonna spend your $, I would look into the Robust comfort rests, now including a curved rest. Yup that's where I spend it.
I'll second what Gary said. It leaves your control hand too far away from the surface your cutting. I like the robust version myself and have made them cheaply. The material is not hard to find and not very expensive.Start with a slice of 3" or 4" schedule 80 steel pipe ,get a piece of 1" steel round bar stock,a piece of A2 drill rod for the top rail and you have everything you need.
Angle iron works also ,if oriented correctly.
Greg
Another agree with Gary. The robust tool rest is very hard steel and will not flex, bend, break or develop rough spots. I would worry about the threads as this at the stress point. If they are slightly loose, it could strip the threads with a good catch. Also, this route is no more costly as you must purchase the bar and the upright separately.
I have a set of these. The main problem is that the diameter of the rods are 1" and so you can not get youir tool closer to the work than 1/2" which is a bit far. I am used to setting the traditional rest right up to the work for maximal support. For small diameter work, this is way too far away. I basically have quit using these rets, altthough I paid a lot for them. Want to buy a set cheap?