I was at boarding school from age 10. Dad was a senior officer in the RAF, and due to all the moving (including a stint abroad) it was my ninth school. I was never at any one school for more than a year, and the shortest I went to one school was 6 weeks. My parents did not "ship me off", they thought long and hard about the pros and cons, and did a lot of research to find a co-ed school so both me and my brother could go to the same one. my brother was 8 when we went. I was there until I finished my A levels (7 yrs) and DB was there for 10 years. During that 10 years my parents moved another 7 times -can you imagine how disrupted our education would have been - different curriculums, exam boards etc etc?
Of course it is not the same as being with your parents, but we had "house mothers" who were non-academic staff we could go to with our personal problems (although how many teenagers go to their parents with their problems?!), we built up very strong friendships that last til today (I'm now 41) despite all of us now living all over the country, and abroad. I got good qualifications and have an excellent relationship with my parents - when I talk about it to friends who lived with their parents during the teenage years, this is something they often comment on.
I think the key thing to remember is not to lump all boarding schools together, in just the same way as you would not expect to lump all state run schools together. There are strict ones, not so strict ones, ones which would suit a sporty child, an academic child etc. It is not a decision to take lightly, but can be the right decision based on the circumstances. I don't foresee that my kids will go, but then I have a very different lifestyle to my parents - I certainly do not exclude the possibility out of hand should the situation change.
It is always a controversial subject - will be following this thread with interest!