I really enjoyed Dokuro too.
I love how it brings so many quotes from so many games into one title (like a Tarrantino movie as a game, only that I know all the games it quotes ), the Castlevania like castle map, the Ico moments, the Super Mario moments, the Mega Man moments, the growing stronger RPG moments. Perfect example of gameplay is the narrative and one of my favorite platformers ever. This and Gravity Daze made the Vita worth it for me already.
As for the difficulty, in the very last stage one of the levels took me like an hour to beat. Then some easier action levels followed but when the next seemingly ultra hard puzzle level arrived I said screw it, I'm gonna use the skip level function (which incidently I rediscovered at the time because I hadn't used it until then) to skip the last three levels before the final bosses. I don't feel cheap (and still had more unused skips left actually), I was just getting impatient wanting to finally face off with the last boss as the game kept adding length to itself. Fantastic bosses too, from the first to the last one.
Very meaty, very challenging, totally unpredictable despite being a best of platforming history, and super enjoyable. Cheap too.