First of all, it is short. I've finished it in 1,5h. It looks lovely. The scenes are really unique. Author really makes art from paper. The puzzles are fresh. I love Machinarium-like games. Played a lot of them. Some of the puzzles were really nice to discover.
First thing, I've loved Limbo. So what you can expect if you have played Limbo: + all Inside's locations have awesome climate + ideas are fresh + puzzles are way simpler + game is shorter If you liked Limbo, you won't regret the time with Inside. The only thing you will regret it's ended so quickly.
The reviews made my bit afraid of the game. Yet I have to say it was around 11 hours of fun for me:) The game recalled the memories of such games like Goblins with abstract and colorful locations (village in the cloud, missions on the spaceship, maiden feast). Most of the puzzles were easy, still item offered to not correct person result with some good dialog. The hard puzzles were on the well designed level -- interesting but not frustrating. I can honestly say the story was good (not great). Definitely worth playing it.