Mechanically, Chantelise is a fairly simple game. Combat is frantic and pretty fun. You lock onto enemies and wail on them with your 3-hit combo, while dodging incoming attacks with jumps or dashes. The most original part of the game is the magic system - enemies drop magic jewels when defeated, which come in 4 different colors. You pick up the jewels and, by mixing the type and order, can cast a surprising variety of cool spells.
Simple doesnt mean easy, though. The game is harshly unforgiving. There's basically no way to heal outside of rare drops, and if you die, you have to start an entire dungeon again from the first room (although you can choose to avoid enemies you've already killed). There's no leveling, so the only way to get stronger is with equips and better play. This is actually a good thing - I expect most people who play the game to be fairly seasoned gamers who will welcome the challenge.
Special mention goes to the graphics - you've got 3D Ocarina of Time like backgrounds, 2D pixel-ly sprites for the characters, and hand drawn anime-esque sprites during story scenes. The whole thing tickles me to no end =D.
The one really bad part of the game is the camera (which you'll unfortunately be wrestling with pretty much the whole time).
The most important thing about the game is that, like Racettear, it has Charm. Sure, a lot of bad decisions went into making it, but everything from the cute sprites to the dialogue (fantastic translation from Carpe Fulgur) to the nostalgic gameplay just come together to make it addicting and fun. I can't stress this enough. Did I mention that the Giant Enemy Crab is one of the bosses? And you indeed flip it onto its back and attack its weak point for massive damage?