http://www.kalzumeus.com/2009/08/01/my-adwords-are-turned-of...Here's the short version of my recent experience:
Half of my business comes from AdWords and I'm pretty happy with it. Actually, you could go substantially farther than that: I'm literally a case study for it, recommend it any chance I get, and despite what I'm about to tell you continue to recommend it.
One day, for no reason I could be certain of, AdWords just stopped serving my ads. Google's automated diagnostic said that you had no credit card on file for my account. That was contrary to reality, as you had already successfully billed me for $300 that week and about $12k total.
I respect that you would rather I use the self-help automated diagnostic, FAQ, and whatnot. But either the diagnostic was broken or your data was, and the FAQ didn't address "What to do if our diagnostic tells you untrue things". So I tried to contact support.
After digging through about 5 separate redirects to get to "contact an AdWords representative", I wrote up a detailed bug report (or as detailed as the 512 character limit would accept) and sent it in. As for what I got back, you can read the above blog post, but it was non-responsive and appears to be computer generated for me.
In the wake of the above blog post and further attempts to use the "scalable communication methods", I was contacted by an AdWords representative. This is now several days after I had first contacted Google. She successfully summarized my issue (which proves that she was not a computer -- an oddly comforting notion to me by this point) and said she would escalate it to a specialist to investigate.
That was a month ago. I still haven't heard back.
On the plus side, the symptom which was of most immediate concern to me (my sales dropping by half because my AdWords ads were not showing) recovered before I missed my entire busy season, and things are more or less normal for me now.