Pros
formlabs definitely does a good job of making the place feel like a fun friend family. There's catered lunches 3 X week (family lunches), and on the other days you can join a soup group. There are plenty of snacks and the building's in a good location close to public transit and has ample parking and bike storage (except in the summer). It's a really cool space. There's internal groups for personal interests (rock climbing, game night, Noms, fernlabs), bi-annual company sponsored trips to an off-site location (ski trip and summer lake house), department/team events, and happy hour every Thursday night. Also as an employee you have access to an unlimited amount of 3D printing and laser cutting. Town hall meetings and family lunch presentations (new employees and department updates) helps keep everyone in the loop about what's going on in the company. They're really relaxed about working hours and working from home, but it's not made explicitly clear as to how much time off you get. There's a written policy of 3 weeks but it always seems like people take off more than that and management doesn't seem to care, which is good but also unclear. As far as the actual work goes, it sure is challenging and there's a lot to learn but it can also at times be unclear.
Cons
I'm not sure how much of a startup it is since they've figured out their business model and definitely are not going to go out of business any time soon. They're still a bit disorganized, more so than other places I've worked at...but what company isn't? When I was hired I didn't have a defined role (good and bad. Good: decide how I want to contribute to the company. Bad: Who's my boss, what am I supposed to be working on? etc). It's gotten better since I started. For examples it can be annoying but also freeing that there are no set ways to do engineering drawings (doesn't call out X spec, or dwg rev vs part revs etc). There's long work hours but I feel that's mostly a vestige of Henry Ford's 8 hour work days b/c it's not uncommon to see people texting, on Facebook/reddit etc. Yes, sometimes (frequently) there are actually times when you have to stay late to finish something and I didn't mind that. It also could have just felt like long hours because some people get in at 8:30 (earliest people start) and others get in at 10:30/11. A lot of "sprinting" time and it makes you wonder if there's ever a time when it isn't "crunch" time. Leaders/management can be passive aggressive and thus hard to get good honest and straight feedback from them. Just gotta realize that for most team leads they haven't worked in many (or any) other companies so they're making up their role as they go (again mixed bag).