In addition to helping you hone your craft, decide between traditional publishing vs. self-publishing vs. epublishing, and whether or not your really need an agent, they can provide you with much needed moral support.
My local group is full of published authors who are great at their craft, and whom are willing to share their knowledge. It's awesome! On top of that, one of them has decided to tackle reading my first book and has told me I definitely have a voice and I'm not as bad at the grammar and mechanical skills as I think I am.
All of this makes me smile, and want to go write. Unfortunately, I'm watching system files copy in my attempt to resurrect an email system for a client at the same time I'm installing virtual servers. The day job pays the bills and is challenging, but one of these summers I'd really like to be able to take a week off, sit by a lake and just write.