There are Kelton, TruCut, Don Geiger's, and new ones from Sharp Fast (Dave Hout may have helped develop?) and Teknatool. There is also the Sorby based on Tormek jigs.
It seems like the Wolverine has been out long enough without improvement that competitors would have introduced a better product by now. I do know that each of these alternatives offers at least one improvement over the wolverine, but I don't know that the end result is an significant improvement.
Has anyone had any first hand experience with any of these?