Either way, I posted some thoughts on this demo at Mario Fan Games Galaxy, but I'll mention them here too:
On the bright side, the level design is incredibly interesting in the beach level I tried out. For example, it's got lots of different secrers and alterate paths, it's massive to the point you never quite know what to expect and really... I like how all these different themes are mixed into one level. It's a bit like what you'd get if you mixed Wario Land with Banjo-Tooie.
The music is really good too. Okay, it was nice when it was posted on its own, but it's ten times better when heard in the actual game. It fits the atmosphere of each section fantastically.
The physics mostly work quite well too, which is nice. It's rather difficult to replicate Wario Land physics in a fan game (as many other people's failed attempts in the past will show you), and for the most part, this game does it really well.
That said, there are a few issues. For one thing, the ground pound needs fixing. It's too slow to be useful, and leaves you wide open for attacks afterwards. Contrast to in Wario Land 4 and Shake It where its quick and easy to 'recover' from and is hence much more useful to the player.
Ladder physics are another issue, I find it very hard to grab a ladder in mid air. Presumably this is because the hitbox is too precise, whereas it should be made a bit 'looser'. Basically, think of a vine in a Mario game. Mario can grab onto any part of it, even the very edge, and the same holds for ladders and vines in Wario Land. In here on the other hand, Wario has to be dead centre or he drops like a stone.
Swimming needs fixing too. Currently you press A to swim up and let go to fall down, which isn't very precise. It'd be better if it was like an actual Wario game, where you just hold the direction you want to swim and Wario just goes in that direction.
Finally, the levels also sometimes feel a tad... empty. Maybe some more enemies would help, or some more scenery in the background.
