I just attended a writers conference this weekend, and during the agent panel (consisting of Kristin Nelson, Becca Stumpf, Miriam Kriss, and Donna Bagdasarian), someone asked: "Can a writer pitch you a manuscript they haven't finished yet?" and in unison they all answered NO!!!
But here's an amusing story. On Friday, during this conference, I was in a critique workshop led by St. Martin's editor Daniela Rap. It was a small group of 8 writers, all of us having submitted in advance the first 10 pages of a manuscript, finished or unfinished, for critique. What a great opportunity to get professional editorial feedback, right? I wasn't expecting the editor to like it enough to ask for the book, especially since its not a genre she works with (I write urban fantasy, she's strictly thriller and suspense). But she did ask me to send her the full, and I had to tell her that what she'd read was all that exists of the book... so far, anyway. She was really disappointed. I felt kind of bad, but it wasn't supposed to be a pitch session. It was a critique! But I told her about the completed book my agent has, so that made her happy and she asked me to have my agent call her right away. Sometimes timing is everything.
Okay, I'm now going to attend as many writer related workshops as possible.