How useful is an Advisory Panel?

Quite some time ago I had a blog dialog with Bill French on the topic of the advisory panels.

The basic concept is that you get a bunch of "domain experts" together on occasion to give you feedback related to your venture. They might be technical experts, markeing gurus, or "merely" good businessmen.

Anybody have any experiences with advisory panels, technical advisory boards, or similar concepts?

Let us know, either here on the blog, or via email.