I was asked to comment here. As you know, I did a data science internship at Impossible Foods in late 2016. I'm mostly jotting down my own experiences, along with some anonymized information from talking to others.

NB: "Tech" below refers to jobs that are considered mainstream tech in Silicon Valley (software, data science, analytics, etc), while "science" refers to the food science/biochemistry/chemistry work that is Impossible's core product.

Pros:

• Highly mission-driven. Many people were vegetarian or vegan (all the food the company served was vegan by default), and people there seemed fairly dedicated to the cause of replacing farmed animals with plants (less than I would expect from a EA or AR nonprofit)
• Diversity. The gender ratio in the main office was slightly more women than men, and there was a lot of representation from different countries that I usually don't see in Silicon Valley (though this could just be because biology/biochemistry draws from a different population than CS).
• Niceness. People seemed really nice to each other a lot, and there wasn't a lot of the assholish personalities I sometimes associate with startups.
• Interesting problems. My subjective sense is that tech there is usually used to support scientific pursuits rather than eg, tech as a product or business development, and is more interesting in a broader sense than most big company or startup work.
• Lots of opportunities to grow. People who're up for the challenge often take on quite impressive challenges at low levels of seniority.
• Benefits. I didn't use them much, but my impression is that the company seemed quite progressive about things like vacation days and paternity leave(?).
• Reasonable work-life balance. This seemed true of the tech people I knew, however the scientists seemed a little overworked and the business development people seemed a lot overworked. I don't know how this compares to other startups.
• The CEO (Pat Brown) appeared highly competent and clearly thoughtful. From my relatively brief interactions with him, there's a reasonable chance he would have been at home in Stanford EA if he was much younger. Eg, he talks about quantitative cause prioritization and had a short rant at one point about selection bias in business advice.

Cons:

• Low pay. I feel like there's a large mission/salary tradeoff that the company makes because it knows it could hire enough True Believers. My intern pay was substantially below market, and this seemed true of the other interns I talked to, as well as full-timers I talked to in broadly "tech" roles. I don't know if this has changed by 2019. Another caveat is that I didn't ask about equity, and Impossible's valuation ~quadrupled in the last 3 years, so it's quite possible full-timers were actually well-compensated even if they didn't perceive it that way at the time. A final caveat is that I'm comparing with other for-profit companies, and maybe a better point of comparison is (EA) nonprofits or academia, and my guess is that Impossible pays better.
• Subpar conflict resolution. I was pretty shielded from the politics as an intern, but I hear more bad stories from others than I would expect from a company of its size (caveat: I have a very poor understanding of the actual base rate of bad conflicts at successful companies). Possibly because of the niceness? I feel like people leave on bad terms more than I would guess.
• Technical mentorship. Because tech is not the main product, you'll get less senior mentorship or guidance than a primarily tech company. (Obviously, the opposite is true if you're a food scientist or biochemist).
• Incrementalist work. Impossible always had a vision of being the eventual replacement of all animal-based products, however when I joined in 2016, it was very much at the tail end of experimentation and the beginning of being laser-focused on beef, which seems less intellectually and altruistically interesting. My impression is that this was much more true as of 2018, however they seemed to have developed pork and fish replacements recently? [1]

Neutrals:

• The company seems fairly high-prestige in the public eye. It's extremely well-known for its size, and people are often excited to talk to me about the work there (in a way that I've never experienced before or since). This seems good for career capital, and well-being, however I want to caution against seeing this as a clear positive. It's easy to fall into prestige traps, and people should introspect about this before they apply. (Also local prestige matters more than global prestige for most job pivots, so public opinion is a poor proxy for how much future employers care).
• Environmentalism. People at Impossible are much more likely to be environmentalists than animal welfare people. Personally I find Deep Ecology views to be philosophically untenable, but obviously other EAs have different philosophical views. I write this so people can make an informed decision self-selecting in.

On balance, I don't think I'm informed enough to judge whether working at Impossible is better than a typical reader's alternatives. My gut instinct is that if you have other altruistic options that can make full use of your skillsets (clean meat seems especially exciting), then it's more impactful to do more early-stage work than being at Impossible, but I'm very uncertain about this opinion and it's confounded by a lot of details on the ground.

Additional Note 2019/7/20: Rereading this, I think people are usually biased against applying, and I think it's still worthwhile for people who consider farmed animal welfare their top (or close to top) cause area to apply to Impossible.

[1] https://www.digitaltrends.com/cool-tech/impossible-sausage-little-caesars/