I watched it on (black-and-white) over-the-air TV growing up in Argentina at the tail end of the military dictatorship. I'm not exaggerating when I say it changed my life -- and many of my friends' too.
I've had my current Netflix disks far too long. Thanks for the nudge; I haven't been able to finish them because I'm finding I need something genuinely inspiring (and interesting).
If you have a media center, you can also watch Cosmos from Netflix Instant.
ooh, and I also recommend Jacob Bronowski's "The Ascent of Man", which is a little older, but it's a similar concept, with a similarly eloquent presenter, focusing on the history of mankind.