My D gets these mailings all the time, too. Phillips Exeter does have an excellent reputation. But you obviously need to make a family decision about whether you think it is right for your situation for her to go.
Davidson just announced a boarding option for the Davidson Institute school in Reno for next fall, too. My D does not know about it yet, and I am dreading the onslaught of begging to attend that will follow when she finds out. For a variety of reasons I don't think it would be the right decision for her. A note about it based on the comment above, the boarding option appears to be with families (not dorm style boarding), so the peer influence might be less at the Davidson program than at a place like Exeter.
You might look out on the College Confidential website at the Prep School section for a lot of discussion that includes Exeter:
http://talk.collegeconfidential.com/prep-school-admissions/ I will say, almost everyone out there is totally sold on the idea that they/their child should go to one of these schools. But if you dig into some of the older threads, my guess is there there are some "pros/cons" threads. And you likely will unearth a lot of info on Exeter that is not in the brochures!