Oooooh, I know; mine are 12, 16 and almost 21, and it never gets any easier to send them off to a new place! BUT, it is so true that, as they get older, they get so much more interesting. As they develop their own ideas and opinions, and become increasingly able to share their views, spending time with them just gets more and more stimulating, and--yes--it gives me an enormous feeling of pride that they're turning out to be such smart, funny, insightful and interesting people.
And don't forget, your little one still needs you, and will for a long time to come (I still need my mother, for a whole host of reasons). When she comes in this afternoon, knackered from her first day of "big" school, it's your face she'll be looking for, and your ear she'll want to fill with all the details. Enjoy!