Okay, so I finally bought this game earlier this summer, and I've been playing for a few weeks off and on, and I beat it today.
I could say a whole lot about it. Like I love the bombchu/boomerang/note taking abilities provided by the touchscreen. Riding on this ocean is wonderful, although I run into whats-her-name way too often. Many of the puzzles are brilliantly inventive (the closing the DS thing made me laugh aloud when I figured it out; I've played Trace Memory but it's been ages). The minigames are lots of fun, the ability to sell treasures and things is a nice idea, boat customization is fun. I loved finding new islands. And this is a loaded statement, but this game probably has the best bosses of any Zelda game I've played (consistently good, inventive, fun, surprising, engaging); considering the quality of Zelda bosses, this means that these are possibly some of the best bosses in gaming, period.
If I had complaints, it's that the encounters with other races (Gorons, the ice folk) were too brief and isolated, when they could have been fleshed out more (like in Wind Waker, OoT, etc). While the final boss itself was fantastic, I didn't feel much of a connection to the boss (hearing about a boss or seeing him a lot earlier in the game make you want to beat him more; you're aware that you must beat him. The game preceding Bellum didn't feel like it was leading up to him.
Also, the game felt rather short (maybe because Twilight Princess was so long). Too much fun to give up yet. But I still have orbs and ship parts to collect, so that'll keep me busy a bit longer.
I may say more later. But I'll join the chorus of voices that liked the game and thought it did something new or interesting, and did it effectively. It's not my favorite 2D Zelda (still Link's Awakening), but it's still a great game and ranks with the best of Zelda.