Nine Nights is quite good. I had a bug that kept sending me back to an earlier area, but it actually worked in y favour, b/c that area contained a chest with 1 of the 5 beads I needed to upgrade my HP bar- and each time I'd get kicked back to the bottom of the mountain, the chest would respawn, allowing me to grind out extra HP.
Once I actually got past that finicky section (the booting me back was happening when I'd die in a certain section, the game went far smoother. Though it then introduced giant eagle riders as minibosses, and I gotta say, FUCK EAGLES. They're always above you, so you can hardly see them, and they are always flanking you whenever you you stop moving, or even just launch into an attack combo on one of the ground enemies. They interrupt your jumps, and the eagle riders took the page straight out of Warcraft and throw thunder hammers at you. Eagles are evil. Wolf riders also suck, but the eagles are pure evil.
Other than that, it's pretty solid. Had to fight another swordmaster, and that fight takes 5-7 minutes each try, because my specials don't work on him, so I gotta keep blocking until there's an opening to combo him back and maybe get a few hits in to chip at his HP. Sword Saint's got nothing on this guy in terms of annoyance.
it's really earning its "challenging" moniker, but my initial impression of "Prince of Persia, but you're a Chinese sworsmaster-assassin" largely holds true. There's a bunch of skills to unlock, but the only one you really need is "jump and then do air kicks". That one nails most minibosses, but there's a few other skills good at clearing adds so that you can deal with the big guys with AoE attacks.