I have tried it, and it wasn't really a positive or negative experience....
There are so many people on these sites that are deceitful with their self descriptions that it makes it a waste of time for a serious dater. Almost everyone thinks they are "fun, easy-going, laid-back, etc etc"..... People basically write on those pages whatever they think you want to hear. Many times, they often post pictures of themselves from 5-10 years ago when they were thinner and skinnier.
Basically, I've gotten quite a few dates from on-line sites, but I always felt like I was robbed of my time.