i have been a member at Low end University for a few months now and it has hands down been worth it for my bass playing personally. i have not used the video submission thing at all as i'm pretty aware of where i suck, but the lessons and lick lessons are definitely getting me in gear.
i've subscribed to a few of the other bass sites like this but Low End is the one i come back to most, as i think the content is organized the best since it's all sorted out by skill level, and Mark is very clear and concise with teaching and straight to the point.
my only complaint (if i absolutely have to make one) is the lack of material for 6-string basses which is what i play, everything is for 4-string, but i understand everyone does not have a 6.