This is a touchy subject. You're not allowed/supposed to criticise your editor out loud (or on a blog) because it's bad manners or bad form or plain bad karma. A well-known romance writer did it a couple of months ago and was criticised roundly for it. If she didn't like the way her publisher and editor were treating her, then she should have talked to them, not whined to the whole world (was the general opinion). There have been occasions where a writer doing this has ended up being dumped by their publisher, but I suspect that the public whinge was only the tip of the iceberg.
On Friday, I attended a day for teachers of Professional Writing & Editing in Victoria (well, actually I organised the darned thing too, which is why I have more grey hairs this week). These days are always wonderful, and we always say "Why don't we do it more often?" but it does take a lot to organise because people are teaching or committed to other work things. This time we had teachers from several hundred kilometres away who made the effort to attend, which was terrific.
Our guest speaker was a supervising editor from Lonely Planet (who, if you haven't heard of them, are one of the largest publishers of travel guides in the world, and they happen to have their head office quite close by). She was a great speaker, and talked all about what they look for in editors, what the application process is - it includes a very hard editing test - and how the company works. She also told us how to become a LP author, which sounded very enticing! But the two skills she emphasised for their editors were project management abilities and being able to have a good working relationship with the authors.
Our students are learning excellent project management skills - this year, they are publishing two collections of writing (Lizard magazine and the student anthology) and in my class, ten of them are creating their own book, magazine or website. They've had to work out a production plan and timeline, and they have deadlines that I give them big nudges about, to check they're up to speed. We're having a multi-launch in 3 weeks.
Working with authors is another skill that we work on with them, but are about to do a lot more in this area. There's a tendency to think the author-editor relationship is adversarial - the editor says Do this and the author has to defend herself. In some cases, it can be exactly like that, which is a great pity, because it often leads to a bad book. A too-defensive author can dig his heels in and become extremely difficult, and foster a reputation for it so that editors actively avoid working with him. On the other hand, an overly-pedantic editor can also be detrimental to a book, forcing changes that might adversely affect voice and style, if nothing else.
The same is true of an agent - many agents these days are expected to act as first editors for their clients, but I've heard of one agent who persuaded a client to rewrite, and then the publisher preferred the original version! It's tricky, there's no doubt about it. As authors, we spend hours and days and weeks and months and years on a book, and having someone pull it apart and tell us which bits aren't working can feel like they're ripping out our guts. But the bottom line is - once it leaves the cosy safety of your home and goes on a journey out into the real world of readers, editors and critics, it has to become the best book it can possibly be before it gets glued irrevocably into a glossy cover, ready for sale. If it's not your best, it won't survive. And maybe neither will you (bad reviews make people want to open veins).
Your editor should be your working buddy, the person who is on your side, the person who wants to help you make your book fantastic, and is probably the best person to see its weak spots. It's very likely you won't be able to! So cultivate your editor, work on the relationship from your side as well, and hopefully it will be constructive and inspiring. And if you have an editor you hate? Don't diss them in public. Don't even diss them to friends unless you trust them. Work on that book, and move on.