I'm going to talk about this from the perspective of a straight male. That's what I am, and I think that's what most of this site's user base is. But, if you're a female, or have a different sexual orientation, I think if you just substitute the gender that appeals to you, nearly everything I say here will apply to you too.
IMO, online dating is super easy to do these days if you can open your horizons to different types of women, and don't mind being passed over by 99% of them. The beauty of online dating is that there are thousands of women in just about any area. So, even if only 1/10% will go on a date with you, that still equals plenty of chicks. I met my wife on PoF, and I had a ton of fun dating before I met her. My sister met her husband on Match, and a bunch of other people I know have had great experiences as well.
The whole key is to contact large numbers of people, rather than to focus on a few that really appeal to you. I have some friends that have taken the latter approach (as that's more like the traditional method of finding a partner), and most have been disappointed. That method leads to feelings of rejection, and few people can push through feeling rejected over and over again. But, if you take the shotgun approach (indicate interest and/or send messages to every person that is the least bit interesting to you), I think its pretty hard not to have success. This will likely take you out of your comfort zone though. Which is probably a good thing in its own right.
So, what are your thoughts on online dating?