Congratulations to your daughter on her acceptances. My DD is in her first year as a boarder at MX and very much enjoying her experience.
Pros for us: strong humanities program (especially Writing Seminar in Sophomore year); scheduling purposefully allows her to do theatre, sing in a choral group, and play a sport all three seasons without having to choose one over the others; the vertical housing which has allowed her to make close friends across all grade levels quickly; the welcoming community with a diverse student body; the advisor system (she has lunch once a week with her advisor who is also a dorm parent, the advisor only has three advisees and so has time to spend with my daughter - and she will stay with her advisor all 4 years!; proximity to Concord with daily shuttles to town, leadership has weathered Covid this year with very little intrusion on her experience.
Cons: the dining hall food (I have mentioned it before in another thread), the math department is a bit uneven, the resignation of the Head of School in October (But under Pro I would list the acting Head of School, Karlyn McNall, who is really wonderful, understated, and well-liked by the student body!); the new theatre and music center are wonderful facilities.
Overall, we have very little negative to say about MX. Of course, it has only been 7 months!