Here is my experience with streaming video having had TW / Comcast and AT&T DSL. Everyplace I have had cable modems, I have had really good download speed, except for those times where I have had real physical connection problems, BUT I also have had trouble streaming video because the connection is bursty and it will pause, downgrade quality, or outright stop working on video that you can't put long buffers on. This was a big problem for me with Netflix on AppleTV. Renting a movie was not an issue because it could download huge chunks quickly and then it could slow down and play through the big buffer.
DSL has been MUCH better because the connection is a more consistent connection. It is not as fast, but for this type of streaming it is a better option.
My connection Saturday played straight through with no interruption and at a very good quality. I have the very pedestrian, one step up from the bottom plan. No complaints from me.