Shantae: Risky's Revenge (DSiWare) 8/10
It is a good sequel and some things were made streamlined over the first game (some good, some bad changes), but the final product seems a bit rushed in comparison (e.g feels like less enemy variety, less dungeons, world felt smaller, less items to buy in store, less mini games, NPCs don't play as big a part as they seem they would). I have a feeling the game being DSiWare and changing the plans to sell the game as downloadable "chapters" and instead releasing what they had as the "final, complete" product probably had something to do with it feeling not so finished.
Even with that said, what's there is good. The animation is excellent and the characters are still charming like in the first game. I clocked in at almost 8 hours to find all the items and beat the game (I went through many areas multiple times). I'd rate the game above Contra 4 (another game by the same company) for the DS. For a DSiWare game, you get a lot value for what you pay and I wouldn't be surprised if it's the best game on DSiWare atm.
If you like old school Castlevania, Metroid, and Zelda you'll probably enjoy this game a lot.