I'm paying for 25 Mbs but that doesn't seem to be fast enough to stream in HD a lot of the time. Just today I couldn't even stream you-tube videos. It seems at least with Mediacom that you may pay for a certain Mb but you aren't guaranteed to get the speed you're paying for most of the time.
If it was steady at 25 Mbs it should be plenty fast. We only have 5 at our house (DSL) and it is enough for streaming in SD, maybe 720P (but only if no one else is online). But we can have at least two, maybe 3 people on Youtube, Hulu, etc watching standard def and it's not a problem.