Pros
I worked at Matter Labs for ~2.5 years as a programmer. I've been there from the early times until I left recently due to personal reasons, overall, I would recommend working there and if given choice to go back in time I would join it again. Some things that I would like to point out: 1. Co-founders of Matter Labs are one of the smartest people I've met on the job, and I would say from my perspective that it's not really common. I've enjoyed having technical conversation about everything ranging from smart-contract architecture, zk circuits to some details of our frontend and so on. I frequently had insights from that conversations that I could not have on my own. There is another good illustration of that: cryptographers (one of them is co-founder) came up with transparent proof system for polynomial commitments (see RedShift paper by Vlasov, Panarin, Kattis). Since co-founders are like that, all hired people tend to follow this description so if you enjoy working with capable people, you may find working there interesting. 2. Company takes crypto space seriously from libertarian perspective instead of cash-grab perspective, privacy, freedom, security, correctness are important instead of token valuation or similar matters. It would be unacceptable to cut corners somewhere and make something “easy to use” by sacrificing fundamental security or other principles essential for crypto maximalists. 2. There are wide range of technical problems that you could not find in other places. People there develop custom cryptography libraries for zero knowledge circuits (people say custom crypto is bad but what if crypto that you need does not exist yet?), compilers, hardware (FPGA), smart contracts along with more traditional projects like blockchain node written in rust, frontend, APIs, etc. 3. The working environment is flexible enough so that you can move around the company if you really want and work on issues that you really like of course there are some constraints but if you are motivated enough, you can do it once in a while. All people are encouraged to think for themselves and to take ownership of some pats of the project. There are little artificial constraints on your career path—if you prove yourself as competent, you can do almost anything, regardless of your “level of experience” or other formal qualifications. There is also enough flexibility, so you can push your vision and ideas to the implementation and feel like you are having an impact, although it's hard to do with critical stuff like smart-contracts and zk circuits because its complex and dangerous but with enough determination and if truth is on your side that is possible too.
Cons
1. Since work is flexible, meritocratic and people are encouraged to think for themselves it may look chaotic sometimes since there are no clear top-down hierarchy that many people love. That seems to be changing though since the company grows. If you want something to be done, you better be proactive about it. 2. There is this zero bs approach that may seem harsh for someone (it does not cross boundaries of professionality) so you have to be prepared to defend your decisions and problems that you work on can be responsible for large sums of money. That is why work there can be demanding compared to other places where you don't have full responsibility over work you do.