For the five people who don't already follow him, Nathan Bransford is a Curtis Brown agent, MG fiction author, and blog-god. Five days a week he writes brilliant posts on all aspects of writing and publishing.
In case you missed his post on Monday about when to hire an editor, it’s a must read for anybody thinking about paying for professional polish of their WIP http://tinyurl.com/yasqpmw.
Here’s a quote:
“The advice should be positive, useful, strike you with the occasional, "Why didn't I see that?!" moment, and, perhaps most importantly, should be consistent with your vision for the project. In other words, the critiquer shouldn't simply be telling you how they would have written it.”