Back an my old house, we had Comcast 25 MB, and it was fine for streaming during the day, and downright unwatchable weekend evenings. I currently have Comcast 250 MB (10x the previous speed), and it is fine for streaming during the day, and so-so for streaming on weekends and at night. In the past I also had 150 MB, and it was fine during the work day for business stuff. In my experience, 250 MB is overkill for 99.9% of business stuff.
If I was only interested in having consistent streaming at any time of the day, I'd go with 6 MB DSL over 250 MB cable.