Without going into specifics due to NDA contract, I will try to be as specific as I can to provide some useful feedback. I was interviewing for a (greater than) senior engineer position (staff in their org chart).
Good experience overall. Work environment was friendly and office environment was modern and new. Engineers seemed competent and relatively experienced. Location is great, in the heart of Boston BackBay.
Phone interview was done through 3rd party company called Karat. The experience there was rather rigid and the interviewers provided no help most of the time... That was actually the hardest part of the whole interview process since everything was so crunched on time and having you do as many technical questions as possible...