What does a writer want from a good editor? What does he or she need?
When a writer looks for an editor, he or she should find someone who not only knows the basic skill set (grammar, spelling, story composition, character development, meeting a deadline, etc.), but also someone who has the fortitude and professionalism to be completely honest about the work. When you get an editor, you aren't looking for a friend or a cheerleader. You're looking for someone to do the hard work of making your work stronger.
An editor has two key functions:
1. Find what's wrong and suggest ways to fix it.
2. Find what's right and make it shine.
You don't want an editor who tells you how wonderful your work is and how perfect it is. But neither do you want an editor who has nothing but horrible things to say about your writing. A good editor will find balance between those two functions and will do the job in a way that may hurt your feelings a little (if you're overly sensitive about your work) but will also make you feel better and more positive about the finished product.