Reviews seem to be pretty positive so far. I'll update the OP as more come in.
Metacritic
OpenCritic
Game Informer - 90/100
Gamespot - 9/10
Game Revolution - 9/10
Gamespew 9/10
New Game Network - 8/10
Game Skinny - 8/10
Slant Magazine - 6/10
Gaming Bolt - 6/10
Steam Store page
PSN page
Screens:
Trailer
Metacritic
OpenCritic
Game Informer - 90/100
Bloober Team's latest is one of the scariest horror experiences I've played in a long time, and its strong sense of place, story, and action put it above the majority of other games in the genre. Observer is simply the best of both worlds and is a must-play for anyone who considers themselves a fan of either sci-fi or horror.
Gamespot - 9/10
Cyberpunk is a reflection of where we're headed as a society, an oddly alluring reality where we've allowed impressive technology into our lives at the cost of our humanity. This is a niche genre that needs new revisions and new pioneers so it can keep evolving as we inch closer to seeing its fictional warnings play out in real life, and Observer adds to the familiar parables in fascinating and unexpected ways. In that respect, and on so many other levels, Observer is a haunting and remarkable achievement.
Game Revolution - 9/10
Observer may only take nine or ten hours to complete, or a little longer if you search through the rubble even more so for collectible cards, and it feels like watching an excellent art house cyberpunk film every second. Its grimy characters, seedy underbelly of futuristic Poland, and uncomfortably bizarre storylines combine to make some of the greatest experiences I've ever had in gaming. It may be a little unorthodox, but it's executed fantastically. If you're looking to be simultaneously terrified and intrigued, you need to spend a few days with Daniel Lazarski as an Observer.
Gamespew 9/10
An audio and visual tour de force, Observer doesn't pull any punches. It would appear that Layers of Fear was simply foreplay for Bloober Team; a warm up for the full-on fuckfest that Observer is. Combining investigation, exploration, stealth, puzzles, and a near constant barrage of horror, Observer is a meticulously created game that rarely puts a foot wrong. If you think you have the stomach for it, this could be one of the biggest surprises of the year.
New Game Network - 8/10
Observer features remarkable trips through fictional minds that unsettle and terrify without relying on excessive jump scares. The nightmares contrast wonderfully with an atmospheric and detailed cyberpunk world that is always fascinating to explore.
Game Skinny - 8/10
All along the way, you will find yourself asking, "Is any of this even real?. There might not be any zombies or giant killers with pick axes, but in terms of unsettling atmosphere and thought-provoking horror, Observer absolutely delivers.
Just be careful because the seizure disclaimer at the beginning ain't kidding either -- if flashing lights aren't your thing, take it easy with this one.
Slant Magazine - 6/10
Whether or not you suffer from simulator sickness, Observer will make you queasy. For better and worse, that's the point of the game, which uses a cyberpunk detective framework to meditate on augmented reality and consciousness.
Gaming Bolt - 6/10
Observer feels like a step down from Layers of Fear. It's intriguing and mind-bending enough for sure with its atmosphere sure to creep out people. But the lead VA, annoying artefacts and some of the horror elements just don't click.
Steam Store page
PSN page
Screens:
Trailer