I was reading this article by Dean Wesley Smith on agents and whether they're required or not, and the various myths that float around them. Some people apparently feel they aren't necessary and you're better off keeping that ten or fifteen per cent to yourself.
Despite having several novels out, I'm no expert on publishing. Most of my writing career has taken place at a distance from my publisher of at least several hundred miles. If I meet them at all, it's at the occasional convention. Julie Crisp has been my editor for a couple of years now, and if I can make it to Eastercon this year it'll be the first time I've met either her or any of Tor's current editorial staff. I've met my agent, Dorothy Lumley, in the flesh less than half a dozen times, most usually when she happened to be up Glasgow way. All I can do is offer the details of my own personal experience of having an agent, which can roughly be summed up like this:
If I hadn't had an agent, I would likely never have got published.
This conclusion on my part largely comes down to the four or five year gap between Dorothy taking me on board and my first novel selling. I wrote my first novel in the summer of 1997, having previously sold a handful of short stories. Dorothy was the second agent I posted that manuscript off to. I first got a glimmer of interest from Tor in, I think, late 2002. At that time I'd decided to go for broke and write a second, third, however many novels in order to break through. I finished up Angel Stations, the manuscript I'd fortunately just started work on, and they bought it.
If it had been entirely up to me to send my novel off to various publishers during those intervening years, I'm pretty sure I would have given up altogether and become entirely disheartened. I don't know how many publishers Dorothy sent that first unpublished novel of mine to, but I suspect it was quite a few. Enough, perhaps, to have persuaded me I was better off giving up and getting a 'proper' job than sending it off again and again if it had been entirely up to me.
Instead the long and laborious process of agented submission, rejection and re-submission took place almost entirely outside of my awareness. In fact, I really didn't want to know just how many publishers might or might not be passing up on my book. So when that first glimmer of real interest appeared, it was a very pleasant surprise.
So are agents worth it? In my experience, definitely.