[legion]

My take:

If you have a truly disfunctional organization, they can be a real asset. They may even be the thing that saves you from disaster if you listen to them. Of course, that all depends on how well they understand your business, which really comes down to the individual consultant(s) you get.

If you are looking for incremental improvements, you are probably better off trying to find them from experts internally. It's easy to find the big mistakes, but it takes someone who really knows your company to find the small ones.