Not too much to add to the comments so far. I have been splitting wood since I was a teenager with something my father called a Monster Maul - there's a few places that still sell something similar. Basically a hollow steel pipe handle and a big triangular block of steel as a head. It will split most anything except elm, really knotty stuff, and the occasional butt log with one swipe. I always orient branches pointing directly toward or away from me - it's easy to split right through the axis of the branch.
My dad has always split 6-8 cords of wood per year by hand, and now that I'm building a house and have an outdoor boiler, we'll combine our efforts. Basically cut and stack about 16 cords a year, and he will get the easy stuff to split, and I'll take the odd stuff and big knotty chunks and toss them in the boiler whole.
I'm heavily leaning toward bagging the entire hand splitting concept and putting a splitter on the PTO of my tractor.
