The game is a side scroller, so I would say 60 fps with the 3D ON on firmware 1.0.0-0.
People tend to have this funny idea that because a game has 2D gameplay, it automatically can't be pushing modern systems.
2D games can still be technically demanding. (Trine 2, for example)
DKCR may be 2D in gameplay but a lot of its assets are 3D models.
I forgot about Trine 2 & Castlevania Lords of Shadow Mirror of Fate.
I can't wait to get Castlevania 3DS after every different review I have read of it.
But I think my next game will be Rhythm Thief & the Emperor's Treasure follow by Project X Zone follow by DKCR3D.
I highly recommend DKCR, it's an amazing game, one of the best 2D platformers since the SNES.
Well, I plan on getting RT&tET this month and then Project X Zone probably comes out earlier in May, and then I know DKCR comes out on May 24, but I might get DKCR as late as June 1 to 3.