I have used these joiners. Although they are not that great with R1 curves, all larger sized of curves and straights work very will with "Uncle Herm's." As others have said, they are a good, but less expensive alternative joiner.
It sure would be nice to have a second source for stainless steel clamps. I tried some brass clamps, but even on my stainless steel, the oxidation was not acceptable to me as compared to solid SS clamps.
Does anyone else but me find the split jaw feature a must-have? It's great to be able to clamp one side, then position the other rail end, and clamp it next without the other (I presume) free to wander around.
Also, the split jaw allows you to undo one end, to remove a switch, for example, and the whole clamp doesn't fall off.
I prefer the SJ clamps for the above 2 reasons, The ability to clamp one side at a time is very helpful especially at switches. In addition, I feel that the split jaw design helps the clamp apply pressure better to each rail, rather than average it to both rails from a single continuous piece of metal.
This design incorporates the singular block design of the Hillman with the triangular grip of the Split-Jaw. For those people that prefer solid blocks on both sides but don't really like the inverted "T" that seems to be prone to cracking, then this might be a good answer! I wonder if the screws are the same as Split-Jaw or Hillman or if there is a third size we would have to get used to?