Color me impressed. I played the original Shantae, though not the DSi version of this title, and while I liked it, it was a bit frustrating. Shantae: Risky's Revenge addresses most of my complaints. It's a fantastic little metroidvania-esque platformer. Great animations on all characters and monsters, warp points to help get around, much better magic/item system, very catchy music, and a much better difficulty curve than the original.
I quite like Shantae: Risky's Revenge. Others have talked about it being a lazy DSi port, but speaking as a first time player, I found this to be delightful. There's so much color and life in the world, it was clear the developer wanted to make the world a living breathing thing, not unlike a storybook, but with better animations. Combat is simple, whip your hair at baddies to attack, transform into different creatures to get through puzzles, use magic as is needed for help or a boost.
Sadly, the number of transformations have been cut down from 4 to 3 from the original Shantae, with 2 returning and only 1 being new. And the game is much shorter than the original Shantae, though that's not necessarily bad, as much of the original was padding. There are parts in this game that can get frustrating, such as using the powers to get over long stages full of instadeath gaps or certain enemies which never seem to go down, but they're relatively minor.
If you are looking for a long game, Shantae will only run you around 4 hours for the initial run and then another 2-3 for a replay with a new mode. It's still very fun for the price and the animation and art style is gorgeous. Gameplay is fun and much improved from the original. Despite my complaints above and the game's shorter length, Shantae has an insane amount of charm and the signature Wayforward polish.
Highly recommended for all platformer, metroidvania, and genie fans. Shantae is a must play.