I loathe Yoshi's Island DS.
Switching babies is tedious as hell. It's Donkey Kong 64 syndrome, where you have to haul your ass back to the character switching station so you can pull the lever that only Donkey Kong can pull and then you go back and switch to Diddy because the lever opened a door with red bananas and a jet pack section
and no.
The game is glitchy as hell. I tried to grab a swinging vine as DK and I ended flying straight up in the air (almost to the top of the level) for no reason. I landed and tried to grab the vine again, and the game froze.
There's absolutely no difficulty curve. Sometimes, some levels are bitch hard, and sometimes they're depressingly easy. I gave up playing the game shortly after beating the Antlion boss - the level itself made me want to snap my DS in half, and when I finally got to the boss, I found it only had one or two attacks that were pathetically easy to avoid.
The best parts of Yoshi's Island DS are the bits that are lifted from the original Yoshi's Island unchanged. Which, at that point, you'd be better off just playing
Yoshi's Island.