Although I'm not usually a fan of Episodic games, this is one instance where it actually worked. I think each level being released episodically is what allowed them to make these huge, detailed maps with tons of options (more than ever before), because they had more time to focus on fine-tuning every aspect of them and designing all the possibilities within them. Some of the episodes are works of art, really. The episodic nature also encourages players to spend their time mastering each level, exploring all avenues, and getting their favourite assassination methods down to a science. That is what Hitman has always been about (except in Absolution). Mastery through repetition has always been a core aspect of the gameplay, and the episodic nature meshes beautifully with that. Right now this doesn't really matter any more though, because it's done. So if you buy the game, you're getting the full game.
The Paris, Sapienza, and Marrakesh chapters are all truly excellent, with strokes of genius. Huge environments with so many fine details, so much going on, and so many things to do. It's almost overwhelming. The Bangkok chapter is good too, but it's smaller and less interesting than the first three, with fewer options. The Hokkaido chapter has a lot of great ideas, though it seems a little restrictive at first. It's much less so once you understand how to properly move around the map, but the level design is a little too confusing and labyrinthine for my taste. Still good though.
I don't really like the Colorado episode though. At the end, it funnels you into one specific area to complete one specific objective, without giving you many options on how to do so. This forces you to plan around that, meaning every playthrough ends exactly the same way, and that feels like it goes against the free-form nature the rest of the game establishes. It does this only because of obligations to the story, and I think that Hitman is best when the story takes a back seat. The level is filled entirely with enemies too, no friendly NPCs. The other levels, filled with normal people just going about their business, feel much more "alive" and perfect for stealthy hits. This isn't to mention the fact that the Colorado map itself is dull and uninteresting compared to the others.
Although one Chapter is a dud, in my opinion, the others range from "good" to "amazing", and I'm a jaded gamer who doesn't use that word lightly. There are some other things that fall flat though... The restrictive DRM, and online-only nature, with your unlockables stored serverside rather than locally, make me worry about the long term future of this game. There used to be server issues, and while it seems more stable now, it can take a while to connect sometimes. I don't see any good excuse for this (singleplayer) game to need a constant online connection. At least make it optional for those that care about the extra features. I'm worried that this decision might make the game a shell of itself one day when the servers are turned off. Another downer is the fact that most of the characters have American and English accents, even though you're globetrotting all over the place. It takes away from the immersion.
But overall this game is true, pure, Hitman. That feeling after pulling off a successful, silent, and creative assassination; then strolling away without anyone the wiser... There's nothing quite like that feeling, and this game takes Blood Money's throne as the new king of it. So now we just need more of this, because there isn't enough. There's never enough. Bring on "Season 2!"...
...Just please make the next one more consumer-friendly, and maybe maintain a more consistent quality between episodes.