I'm 32 and Mum and Dad seperated just over 2 years ago.
We are a much happier extended family as are my parents. obivously primary concerns were their happiness and I am convinced they are. They have both become much more 3 dimensional people - getting more hobbies, friends, life aims etc and their energy goes into living a full life rather than struggling to live together. Our second (selfish?) concern was how family get togethers would be, Xmas, being Grandparents to our daughter and I am so proud to say it is fantastic. They get on grand when we are all together, and they are good friends. When ever our daughter sees one of them the other joins for dinner or a trip out etc. it has made getting to knwo them individually and one who was slightly dominated in conversation by the other I now chatmuch more with.
One has a daughter from a different relationship and that has become easier (long story and it isn;t mine to tell) and the other now has a new romantic interest and both chat more about them to each other.
It was werid at very first though so much easier than when it happened temporarily when I was a teenager. Emotionally it fel tthe right thing, they were immediately happier etc but also (selfishly again?) as us kids were settled with our own little family it didn;t feel like we were being ripped apart.
it would have been very very different if they had parted badly though....