I finished Firewatch last night, only a bit later than everybody else on the planet. (Catching up!) (I am not in fact catching up at all.) I see that Jmac has already posted about it, and I don't have a whole essay's worth of thoughts. So this will be a bit of a response post.
My immediate thoughts upon finishing the game:
Firewatch was a nice little story game that worked well for me. I enjoyed walking around in the slightly-stylized wilderness. The park was big enough for me to explore over a few days, but not so big that I got tired of crossing it (in a given chapter) or inhabiting it (over the whole game).
The designers had a great sense of how to vary the feel of the environment. Different "biomes" had different color, texture, and audio palettes. Time-of-day changed the environment, which is old hat; but FW had the additional axes of season (beginning of summer to the end) and the slowly-encroaching wildfire.
Yes, I had a sense of compression -- it was a pocket world made up of micro-worlds. But that's appropriate, really. I didn't want to spend a real-life week hiking back and forth. Similarly I appreciated the magical map locator. Yes, orienteering would have been more realistic without it, but I would have gotten fed up with that aspect of the game quickly.
The biggest strength of the game, obviously, is the voice acting. The biggest weakness (for me) was the midgame tease of the "you are a psycho" trope. I spent a fair part of the game thinking "Oh, they're going to do that damn ending" and disengaging from the story thereby. In fact they didn't do that damn ending -- spoilers, you are not a psycho -- so I got back into it towards the end. But it was a misfire of the story construction.
I also felt somewhat harassed by the radio-response UI, which was notably terrible on MacOS. Momentum scrolling made it difficult to stop on a given choice, especially with a short time limit, especially if the frame rate was down (as it often was on my middle-aged iMac). I feel like one particular misclick changed the whole ending of the game -- that is, not my character's ending, but the interpretation-of-what-happened discussion that occurs at the end. So that was annoying.
As for the overall narrative structure... FW doesn't push any particular boundaries; it grabs some familiar structures and makes a good job of them. E.g., the interpretation-of-what-happened discussion at the end. Or the way it reflects dialog choices into the game world later on. Or the game's introduction, which is not just CYOA-style IF, it's practically a Twine clone. (For example, it adopts the convention of highlighting the last few words on a page as a "next page" link, rather than having an explicit "click to continue" button. This isn't something inherent to Twine, but it's evolved in Twine story-game culture.)
That's all I've got. Glad I played it. Glad it was the size it was.
Now, onto Jmac's post, which I see is also about pacing...
Well, I didn't have the same problems. The transition to the focus on the two lost campers was kind of rocky, yes. But the game offered it up and I went with it. I'm generally complacent when the author gives me a push. (That's why I'm terrible at reading mysteries. I'll follow any misdirection without complaint.)
I did feel that the game did a poor job of linking together the two backstory-stories: the protagonist's sick wife and the lost campers. It's not that either of them disappeared from the game; but when one came up, the other faded away, and vice versa. So there was a disconnection there, but it wasn't between me and the scenery.
No, I did not find the cabin. Yes, I adopted the turtle. Then I forgot about the turtle until the last day. That could have been kept more on-surface. The turtle was fine, don't worry.