As much as I fancy the world of the Moomins, the game has some major flaws, that you should know before buying.
Instruments
Firstly, the concept of three instruments wielded by the protagonist is pleasant, it is a wasted potential for it to have available only one song per tool (apart from the drum, as the player can set the rythm himself). Songs are soothing but repetetive, and gaining new levels should allow Snufkin to enhance his repertoire. Very simple solution to very basic issue, rewarding the player with something more than just a level number in the corner. It screams out for Snufkin to be able to play anything else than just basic tunes, and sadly it's all you get from the start until the very end of your journey.
World-building mechanics mistakes
First very irritating and irrational decision is to lock the gate of the fence, after you visit a certain character in her house it's Mrs Fillyjonk . If you move forward with the plot, the gate closes itself forever, locking you out of the literally longest single route on the map. Problem arose, when searching for findables and such, I wanted to make sure that I checked every corner, so I followed the same path only to find the closed gate. While you cannot get across or travel in any other way, the only way back is to follow the mundane path back, severly unsatisfied with how this was handled. I just cannot imagine what caused this decision, as this bring little help to non-existing problem from the player perspective, only causing irritation or confusion. For such a short total gameplay this adds just a substantial waste of time.
Second, more major issue is that one chapter of the game takes place on an separate island. If you miss anything there before leaving, it is locked for you until next playthrough. You have to repeat the entire game, instead just allowing the player to visit the island after you finish this chapter, solely for the purpose of finding anything left behind. Again, very simple solution to very basic issue. From the game-making mechanics it's a faux pas and laziness in execution, especially that this title should bring rather cozy couple of hours, devoided of such simple flops. Which brings me to the next issue below.
Achievements and bugs
As much I am not the "achievement dog", i'd imagine completing this game 100% is not to hard on the first and only playthrough, taking into account that the game itself is not difficult, so i wanted to do it just for pure pleasure. However, with the issue presented before, I cannot complete the game entirely unless making sure I sweep every leaf and corner on the location that i cannot get back to, and sadly several achievements simply did not pop out for me, despite of meeting the terms (Run for the Hills for instance). Bugs with such a short title is just sad, as there is no much things to get broken, compared to big titles on the market with multitude of variable factors.
Laziness and lack of conclusion
There is a thorn in my side on handling the ending. While it is not rare thing, to save player progress to the certain checkpoint and "travel back in time" after you reach the ending, to be placed just before final sequence, I was very disappointed that I could not travel across the Valley after taking down the dam. With massive part of the map being the dried river, the game begged to be able to finish the side quests or simply sightsee while the water is flowing again, especially that the player is never getting down to the ditches, so mechanic-wise nothing would change. You still travel across the bridges, logs and stones, and just like with the progress on the instrument playing, you receive no reward for your efforts.
In conclusion from the perspective of the player, you receive:
Quite ruined and not nice looking areas after totally demolishing the parks. I get the message of releasing the nature, but in the end you just walk across the rubbles and destroyed pieces of fences until end of time.
No visible reward for the final chapter (that could be achieved by putting some water in the dried river), just roll the credits and we're done.
Conclusion
While the game has some unquestionable charm and quite funny moments, especially the Snufkin not giving a **** on some circumstances and having some mild "bad boy" outbursts - via dialog or actions - in contrast of his stoic nature, there is some missed potential with such a rich and vast world of the Moomins. The game has very short lifespan and there is nothing wrong with that. I have enjoyed shorter titles. But with the issues presented above you should totally not buy it for a full price. Prices of downloadable content is laughable as well in my opinion.
My advice: Get only the standard game with substantial discount. Get ready for 2 playthroughs if you're a perfectionist. Otherwise I cannot promise that you will feel somehow allured and disappointed in the end.