My picture quality really did not change much after this box. Picture quality in analog is fine (channels 2 - 99). However, as you would suspect, the digital channels (101 and up) are a substantial improvement over analog (in some cases, equal to DVD quality). The thing that I have been most impressed with the Explorer 8000 is the quality of the recording of digital channels. I had several relatives over recently who honestly could NOT tell the difference between a recorded digital channel and a live one.
Analog audio quality is good. For some reason, if you play analog channels on a delay (e.g., watching them recorded - even a brief delay), quality of sounds appears to be better. I think this has to do with the fact that a recorded analog program's audio is converted to digital by the box. My Denon surround receiver has Dolby Pro Logic II (along with Dolby Digital 5.1), and it does a pretty good job with an analog stereo signal. Of cource, the digital music channels (MTV, VHI, etc.) are awesome.