Amanita Design is well known form its delightful Samorost games, which are free; with Machinarium, they've basically taken the aesthetic of those games, produced a much larger one (about six hours of gameplay), and are offering it for sale, along with a playable Flash demo that's an excellent little game in its own right.
Amanita is a Czech studio, and their games have the hallmarks of Czech animation: beautifully drawn, somewhat melancholy in terms of story and emotional feel, and wordless. The game itself is a conventional point-and-click graphic adventure, with an inventory and inventory combination (something the Samorost games didn't have). The puzzles are charming, if in some cases moderately obscure; one feature I'm not sure I like is that while the cursor changes over hotspots, which makes it easier to figure out what to do, it does so only when your character, a robot, is sufficiently close to the hotspot to interact with it, so you spend a fair bit of time wandering around each location simply to determine which bits are clickable.
One other nice feature; at any location, you can ask for "help." Rather than providing hints or a walkthrough, what this instead does is require you to play a rather easy little shmup minigame which, if you win, provides you a walkthrough for the current area, in comic-book form. Since playting the minigame takes a couple of minutes, this disincentivizes you from reaching for it the instant you encounter a problem, but does provide the solution should you feel you really need it.
Amanita seems to have put considerably more effort into Machinarium than into the Samorost games; not only is it much larger and longer-playing, but the level of detail in its painted scenery is intricate and impressive, and the puzzles are more complicated and imaginative than in the previous games.
Machinarium is beautiful, haunting, strangely evocative of its alien world, often frustrating (in a fruitful sense, as all good puzzle-based games are), and to my mind well worth its $20 price point. At a minimum, give the demo a go.