The Outer Wilds DLC adds a fascinating new area to explore, the Stranger, with a very cool design and visual style that I enjoyed. The lore of the new content is well-thought out and (eventually) ties in with that of the main game very satisfyingly. Echoes of the Eye also adds some nice new puzzles and mechanics for the intrepid explorer to investigate, especially those centering around light and shadow. The new music is as excellent as always and helps build the Stranger's rustic, yet decrepit and melancholy ambience.
Unfortunately, despite these strengths I can't recommend the DLC. It makes several design decisions that are at odds with Outer Wilds' core design and strengths, which in my opinion detract greatly from its enjoyability. First and foremost, the Stranger is at least as large as any of the other planets and must be traversed entirely on foot; you can't bring your ship to its surface, which is mostly intended to be explored in a one-way loop, with few shortcuts. Traversing the new environment is interesting and new at first, but it eventually gets quite tedious and feels like it takes far too much time. Compared to the base game where you are free to rocket between multiple planets and land where you please near points of interest, traversing the Stranger after you've learned your way around feels slow, tiresome, and repetitive.
The size of the Stranger size combined with the necessity of leaving your ship behind to explore it also means your ship log is much less useful now. In the base game you will return to your ship multiple times during a loop and have abundant opportunities to update and check your ship log; in Echoes of the Eye you will usually only be in your ship at the start of the loop before ditching it to probe further into the Stranger, and have to go out of your way, well away from your objectives, to return to it. It would have been really nice if the DLC gave you the ability to check your log while outside your ship.
The difficulty in updating and checking your ship log ties in with another design decision which I found interesting but ultimately a net negative: the almost complete absence of readable text in the DLC. There is not much written text on the Stranger, and it is (not surprisingly) not translatable like Nomai writing is, since you are the very first Hearthian to see it. Instead, you learn virtually everything about the lore and new mechanics from environmental clues and pictorial slide reels you find around the Stranger. In the end I still enjoyed the new lore, but in terms of figuring out the mechanics and what to do next, I found this approach left Echoes of the Eye feeling much more opaque and occasionally frustrating than the base game.
This frustrating opacity was nowhere more evident than in probably the most controversial design decision of the DLC, the addition of stealth/survival horror-like segments where you must sneak past undefeatable enemies without getting caught. These segments are pitch dark, with your only illumination a weak lantern that alerts the enemies to your position when used, but is your only hope of navigating the mazelike levels and seeing your otherwise invisible pursuers. These sections were incredibly unfun and felt like a drastic departure from the gameplay loop I enjoy from Outer Wilds. I was hoping and expecting I would discover some secret or trick to make them more manageable like with the anglerfish in the base game, but there is no such trick. The developers kindly included an option to make them easier, but for me this simply downgraded them from impossible and terrifying to unenjoyable and stressful. I don't like horror games, and I didn't appreciate the addition of these elements.
The stealth segments in particular, and to a lesser extent the Stranger as a whole, also clash with the basic time loop mechanic that Outer Wilds is built around. There are some time-sensitive effects on the Stranger to make things more interesting, but for the most part the time loop simply feels like an annoying limit to your exploration before you have to go through the tedium of flying to and traversing the Stranger again. You are apparently expected to figure out the aforementioned stealth sections via (literally) blind trial and error; the extra time pressure only made them even more frustrating and stressful. I tried them dozens of times across multiple loops, feeling like I was learning virtually nothing. In contrast to the base game where you will often end a loop early to check on something that happens earlier and connect the dots, on the Stranger I only ever ended loops to get more time for more attempts. The annoying inability to use your map on it also makes it difficult to tell how much time you have left.
If you loved the base game and find the DLC on sale, you may find it worth it—especially if, unlike me, you enjoy the kinds of survival horror games the stealth sections seem to be based on. I have much more mixed feelings after finishing it, and in the end I wish I'd heeded the warnings of others about Echoes of the Eye.