Ugh, angry customers. I worked in the computer lab at a local college for a while. There was a girl that would come in at least once a week, and she was beautiful. Early one morning she stormed in swearing like a sailor, ranting that the testing center wasn't open yet. She went from a 9 to about a 3 in less than 30 seconds.
On the other hand, there's Sony tech support, who were so rude to my sister, recovering from cancer, that they made her cry. In a completely unexpected turn of events, Circuit City, who she had an extended warranty with, was willing to fix the laptop after only one call, and they had it back in under a week. It'd had a bad motherboard for months and Sony wasn't willing to do anything about it. You'll never catch me buying a Vaio.
Comcast support around here is maddening. They always assume that the problem is on the customer's end, and if they send someone out to check, they'll bill you for the time, even if they find nothing wrong and the problem persists. The problems keep getting worse too. Channels randomly drop out, get funky colors, lose captions, audio volume rises and drops, etc.
Then there was an online store I bought a game from (Purplus). When it came the first disc couldn't be read. It took about a dozen emails, each of which was responded to with generic insructions that ignored what I told them, before they authorized an RMA. They kept insisting that some systems couldn't read the second disc because it was a two-layer DVD, completely ignoring that I was having problems with disc #1.
Then there's the fact that just every video card maker I know of takes months to replace a defective card under warranty, and none of them cross-ship. *sigh* ATI did back when I bought my Radeon 7500, but I don't think they sell cards themselves anymore.
Companies that have given me good customer service, beyond what I expected, when I had an issue include: React (makes console accessories), Newegg, ATI and Crucial.