This game is gorgeous. Let's get that out of the way first- it is absolutely stunning. And with about three hours put into the game and 100% of the achievements obtained, it's a good game for achievement hunters as well. If you're looking for a pretty game to sink a few hours into, then you could do worse than Sparkle 2 Evo, especially when it's on sale.
The sound track ranges from the advertised 'relaxing' to 'wasps in eardrum' noises that made me check my speakers, but that may just be a matter of taste.
It's in gameplay itself, and execution, where the game could've been great, but turns out to be just mediocre. In the beginning you're presented with the idea that eating certain types of food within the game will change the way your Spark evolves. This could have been very interesting, with different tactics for different branches, but the only difference in the 'food stuffs' is color. So yes, you can eat a non-meat fish. Maybe it's swimming algae. Even with the vivid color scheme, it can be difficult to tell which of the more advanced creatures correspond to which color without some trial and error.
Finally there's the 'boss battles'. The bosses do not fight back, and one of them barely moves- victory consists of slowly nipping suicidally-depressed mega-fauna to death.
But hey. It's pretty.