I just cancelled my Time Warner Internet a few minutes ago (switched to FiOS). The call took all of 8 minutes and the rep didn't put up a fight at all. I joked that it might actually be worth continuing to pay $50/month to avoid the hassle of canceling, so this left me pleasantly surprised.
Once I moved and realized I forgot to turn off my phone and DSL. The company did it in minutes over the cell phone. I was surprised, and a little worried, by how easy it was.
Cancellation isn't always a nightmare, even for companies with bad practices. But it's luck of the draw, and your luck can run out at any time, at least while government continues to stall on adequate consumer protections.