Flexibility, work-life-balance, some of the benefits are nice (stayfit reimbursements, donation matching, 401k 100% match, unlimited time off, etc.), lots of internal technical resources so you don't have to reinvent the wheel.
Cons
Pay is less compared to FAANG companies, I've seen people quite Microsoft due to bad managers (so happiness may vary based on teams), work-life balance can be bad during some crunches, live site support will be mandatory if you work on the web.