Don't listen to Gamespot.
And unlike what the review suggests, the underground parts are far less prominent than the above ground parts, the environments are varied almost throughout the entire game world, with rather minimal repetition compared to most side scrollers, and they used a screenshot of an underground section in the review that's probably the worst example of how it looks in the entire game. There are usually beams of light in the background, cracks that peak outside, houses from the abondoned town, etc. To me, calling any part of the game drab is just a description that doesn't fit. The art and environments are gorgeous throughout.
This game is the definition of the perfect downloadable software. It has the production values of a retail game, the length is good considering that you're getting a retail quality game at a fifth of the price (plus a little bit extra you can do after you beat it, if you haven't already), the gameplay is innovative and it's catered to the system. Controlling Toku is very fun, and the expansion of your moveset throughout the game is very Metroid-esque and is succinctly satisfying. The length is actually comparable to Metroid for the NES, which is $5 on the Virtual Console, but the game and its design are far greater (at $5 more). They're similar games in terms of design, and Metroid fans will likely love LostWinds.
This is among the greatest efforts of third parties on Wii. Of course, you're getting an installment in what will become part of a series, but you're not paying for an entire game. This is like one of those really clever indie games but with production values much higher than most indie games. If you want an interesting platforming experience, it's a must-try.