Comcast - What's the difference in speeds?

I have a question for all you smart computer geeks out there. I have my service through Comcast and pay $42.95 a month for the fast speed. A friend just told me that she was paying that with Comcast but now has gone down to the slower speed and is paying $24 a month and she can't even tell the difference. She said you only need the faster speed if you are downloading movies or music. Any opinions on that out there?