I think having Ortho layout makes using the numpad on the Kinesis a lot better. The big ergo benefit to me is the thumb clusters and the fact I can remap keys like (),[],{},~ to be easier to press. I have setup the "delete" key on the thumb cluster to be a layer shift and moved symbols to easier to press fingers than ridiculous pinky extensions. The numpad is also easy to use since I just hit delete and then it's already under my right hand and I don't have to move it. Since it's Ortho it feels like a numpad. Previously I never really used the numpad because I didn't like moving my hand over but now most of my numbers are typed that way.
I don't think MS/Logitech boards go far enough even in the split department.