I'm the world's biggest skeptic so I bought an X25 in late May to see what all the hype was.
I'd been using a Sotz Monster Maul almost exclusively for 30 yrs at the time,occasionally my old Plumb double-bit or sledge/wedges for the stubborn or extra large ones.
I LOVE IT

Easily 70% of the wood I cut is dead Red/Black Oak,with the remainder White or Bur Oak & Shagbark Hickory.Since I got it I've split about 9 cords approximately.At least 95% of the Red/Black splits with one strike,except for the rare spiral grain or knotty one.Even dead 4-5 yrs. The White Oak is much more stringy,most of it over 7"-8" I have to break out the big maul.What Hickory I've found so far the X25 works almost as easy as the Red Oak.
Will be getting an X27 before too long.