I'm using the Digital Rapids 500 card and the base level Stream software. I like the real-time encoding, but I've struggled with a problem:
Whenever there is a true black (fading in, for example) the "black" is really a noisy, moving swirl of artifacts -- very dark gray, ugly and disturbing. I've noticed that using a higher bitrate makes the black a bit blacker and less noisy.
I have seen this in encodes from other sources as well. I've considered changing all my fade-ins to dissolves from a dark texture, which seems to work better.