About Informational Interviewing

I frequently see job seekers who feel they could really use some first-hand insight into a position before they're comfortable making a major career decision, but I rarely see people who have already begun the process of informational interviewing.  This is one of the most useful tools out there for field research and one of the most powerful networking strategies, yet it often gets completely overlooked in the career planning process.  I recently had an article on Philly.com discussing some basics of how to get started with an informational interview.  If you've been on either side of the informational interview - as a prospective candidate or seasoned professional - what's your experience been?