Tom Evslin with yet another meaty post - this one on why subscription pricing is a good thing.  Money quote:

Customers like subscription pricing. In fact, they are willing to pay a premium for predictability and simplicity. If you can find a way to price a service at a flat monthly rate, you can make a better profit per customer and attract more customers than if your pricing is based on reading a meter. You also save a fortune in detailed billing, dispute resolution, and issuing credits.

Much more in the post.