I did it twice ... One time for a long weekend in New Orleans and another time for 5 days, when I got married in Vegas. I didn't think it was appropriate to bring a 6 year old in Las Vegas ... besides it was my wedding / honeymoon didn't exactly want to spend my wedding night with my daughter sleeping in the next bed ;)
DH and I went on two duo trips when DD was 1.5 and then 2.5. It was nice, but she's old enough now that just about anywhere we want to go, there are things we want to show her and have her expeirence too. Talk to me in a few years ago when we haven't had an overnight without her and I'm sure my story will be different! LOL
I've been on two trips without my dd. Once when she was very young I went to Cozumel with my best friend for 9 days. And just recently, my SO and I took our first alone trip to the Keys. Key West was definitely no place to take a child, we were gone 6 days. Other then those two every vacation I've been on she's come too!