The best relationships contain both.

I beg to differ on the remaining friends bit ... I know for some it works, it all just depends on the relationship you had and on how you split up.
If a guy is controlling, I don't see how remaining friends can be good.
It will hurt. Remaining friends can make it difficult to let go, meaning you cannot move on, not get over it and not get ready to find new love in time. I think especially women can find it difficult to remain friends and to really let go and move on at the same time. Being friends will make it too easy to latch on to hope of getting back together.