Amazon streaming bitrate

I just thought I'd post this here, as a Tivo qualifies to stream Amazon Instant Video. I am wondering what the typical video bitrates turn out to be, both for HD and SD streaming (as I see both are being used). I am interested in whatever anyone might know about the bitrate of the actual video, as well as the incoming transfer bitrate. Does TWC internet service bandwidth-throttle Amazon like they do Youtube?



Thanks

Chris