In the relatively short time it has been around, Machinarium has become a classic game in the "point 'n' click" genre. It stands with the best of them.
The art style has a lot of character. Every backdrop, every item, every character has been lovingly designed and the art can tell it's own story. Even though there's no "dialog" (characters' speech balloons are short sketchy cartoons), every character is very loveable, even the bullies. The music and sounds of the game are similarly well crafted. It is clear that music is put on high pedestal by the creators of the game and it is better for it.
But what really stands out are the puzzles. Every puzzle is clever and there is a definite sense of accomplishment after solving it. What's more, I never felt like there was a "repeat" of puzzle. Each one was unique and challenged me to think in a new, novel way. I'd love to give examples, but that'd spoil some of the fun!
Also worth mentioning is the hint system. In the top right of the screen, there is a hint button that offers a single hint for an area. Usually the hints give direction as to what the immediate goal is, which is especially useful if you ever find yourself confused by what you should be doing. You still have to figure out how to reach your goal, though. There is also a kind of "walk through" in the top right corner that can be accessed at any time if you get really stuck. It gives you more details in an almost comic book form. If you're worried it'll ruin the game, though, fear not! The walk through is locked and the only way to unlock it is to play a short horizontal shooting game, which isn't terribly easy. You must do this every time you want to open the walk through. If you're tempted to cheat, it's much more convenient to find a walk through on the internet. The hints definitely do not spoil the game.
Word of warning: this is a slow paced game. You will often just be sitting still as you try to figure out what to do next, and when you figure it out the event often unfolds slowly. The pace can soothing and relaxing or it can be annoyingly slow if you're impatient. Just know what you're going into.
So overall: great visuals, great music, great characters, great puzzles. Easily worth $10.