PLEASE, PLEASE, PLEASE take advantage of every opportunity you have to get feedback. Most of us work on the same story for a long time. Carol started this blog because it's so hard to find people willing to look at your work and give an honest opinion on what's working and what isn't. Right now Unicorn Bell is new and our number of submissions is small.
Take advantage of this!
If you want to become a published author, no matter which path you choose, you must get eyes on your writing. You guys can submit the exact same 250 word opening as many times as you want if you still want another opinion on it.
Also, your book does not have to be finished before you work on your pitch. Many people start with a pitch before they start writing the book.
So send in those pitches people!