Here's what people have asked and answered about working for and interviewing at Fitbit.
They are growing fast and stable
I interviewed for the position of embedded s/w engineer. The process is unnecessarily long and consisted of an hour long initial phone interview with HR, hour long on-line coding test and phone interview with a s/w engineer. After "passing" the coding test you will be asked to solve a programming assignment and email them a zip file with your solution, Makefiles and short write up. This takes at least a few days. Passing this gets you invited to the day long on-site interview where you have to answer technical and programming questions from at least 5-6 engineers, many of whom are quite condescending and arrogant.
Its a great place for a job, but not if you'd like to have a meaningful career. You don't go there for the money.
You meet passionate people that are below manager level, but manager level and above are more cutt throat
Slow progress on projects. Way to many meetings. Projects miss deadlines and lots of mishaps due to poor project management and inexperience from manager and director in my department.