The value of the feedback you receive is not necessarily related to the writing skills of the person you're consulting.  That person may have insight into that particular subject area or into how the audience might react to your message.  This can be a lot more valuable than having someone simply correct your style.

One of the keys to using feedback effectively is to remain open to new ideas and new approaches.  And don't be defensive.  Many years ago I rewrote a book on HMO capital financing for the CEO of a boutique investment bank.  Unfortunately, my client wanted to meet once a week to discuss every single comma change, and he was highly resistant to any alterations, which of course defeated the purpose of hiring a professional writer.  The argument that "that's just my style," only gets you so far.

That being said, one should recognize that not all feedback is equally valuable.  It's usually not very helpful if people come back and quote you the rules of Composition 101, especially if you're already a fairly sophisticated writer.  Long ago I had a boss who would read whatever I wrote, and rather than commenting on the content, which is what I needed, she would make dozens of corrections to my grammar and style.  The irony, of course, was that she had only the vaguest idea of either.

So what do you do if you sometimes get feedback that isn't helpful?  It may be a good idea to consult different people for content and for style.  Effective writing is all about strategy, which is much harder to get right.  Naturally, you want your writing to sound good, but if you use the wrong strategy, it isn't going to matter.

It's helpful if you give people specific points to respond to.  "If you were one of our clients, would this persuade you?"  "Is paragraph three clear?"  "Do my arguments follow?"  If you get them to focus on what you most want to know, you will get comments that are a lot more useful than, "Sounds good to me."

Also important is including a timetable.  How often have we all gotten feedback that was too late to use?  Whenever you are requesting information, in fact, it's useful to say when you need it.

You may also find yourself in the role of feedback-giver.  If someone comes to you with a piece of written work, think of what it is they really need from you.  Giving feedback is not a forum for stroking your ego, and your goal should be to help make any document as effective as possible.