IRS
Evan mentions that the IRS is giving suprisingly good customer service these days. I've had some mixed results with them. While the people I've talked to have been very helpful while on the phone, their follow through was just not that adequate. Up until recently I'd been dealing with a problem where an old company I'd worked for had misreported my pay by a few thousand dollars and never notified me of this.
So, about 2 years ago I got this notification that I owed money. Lots of it. And I went to go about fixing it. I got revised forms from my ex-company to correct what had happened. And I sent/faxed numerous copies of it over the course of those two years. There is not a record of ANY of them ever being received. One of the issues here was that they told me I wouldn't hear anything for two or three months. So every time I sent something in I just had to wait. They made it sound like whatever I sent in had to float through a few departments before it would be resolved.
So finally one day I was completely fed up and the person I was talking to at the IRS sent me over to the Tax Advocate. This is the department that handles problems that just aren't being solved.
About a week later I got a call from a very nice lady who listed to me relate my story for the 10th time or so. She had me call my ex-company and have them fax her the paperwork and that she could handle everything from her desk. Two weeks later I got a letter from her saying it was all fixed.
Now, while this woman was amazing and I'll be forever grateful to her, I wish I'd been able to talk to someone like her from the start. She was the person who understood best what went on, and was able to action on it immeadiately. I wonder if there isn't a better way to match up cases with mine with people like this more rapidly.

(Of course, then I had to take care of California too, since they'd gotten the same initial tax information. But that's another story.)