That's actually a pretty good plan. If they are truly protocol agnostic they won't get into trouble for stomping on data which is in competition with their own products (sorry your Skype does work, but maybe you will consider signing up for Comcast's phone system). The 250 GB / month with an easy to handle step for more data is good, although they should add an easy way to track total usage so far in the month and a way for the customer to choose if he wants more data instead of assuming an automatic billing for it.
If you streamed 128kbps MP3 music for the entire month, that would only be about 41 GB of your 250 GB allowance. (assuming they have their bits and Bytes labeled properly).
although they should add an easy way to track total usage so far in the month My thought too...because the problem I see is this;
Comcast says I'm over my bandwidth limit of 250Gb by a total of 20Gb and I owe them $30.
How am I supposed to know that they are correct or being truthful? And what proof do I have that they are trying to shaft me? They've done it before with their other services. It will happen with this as well. Count on it.