To future empty nest-ers: I decided early that I would go into my empty nest with a positive outlook -- I turned 40 the year my only child moved out, and decided that my life was finally going to be my own. That's when I started getting involved in things that I was interested in, and hey - I could finally afford to do them! I still felt the empty space from time to time, but as long as I can call or e-mail my daughter once in a while, my heart feels good about the situation. And, we've become good friends now that I'm not "the boss of her" anymore! 
Yeah, your relationship with your kids changes dramatically when they grow up . . . er, uh, get older (sometimes it takes a while to grow up). I, for one, never intend to grow up

. Life changes, and there are great things to be had when your kids are no longer your primary responsibility. When I turned 50, I finally wrote a book and learned to dive. Now I'm an artist (remember, it's in the eye of the beholder!), and I can afford to spend some time and money on me. Then, if you're really blessed, they'll marry and have grandchildren - and it sort of starts all over - except you get the fun part without the responbility. Our daughters have given us 3 granddaughters, and we finally have a boy on the way in October.
Yeah, it changes -- but change is good