I'm not sure why nobody mentions this, but for windows and linux, you can fiddle with a "split keyboard" by using two keyboards. You can put your right hand over the right part of the right keyboard, the left and over the left part of left keyboard, and ... type away. It just works, and usually it is free, almost everyone I know has a pile of keyboards somewhere.

Irritatingly, this doesn't work by default on the mac where the meta keys only affect the keys on the keyboard owning the depressed key (IE left shift and right keyboard l will not result in L).

It uses a bit more desk space, but is otherwise a pretty good way to test out "do I want a split keyboard?"