I've been reading /. for ages and ages. For me the key to avoiding the frippery that can consume the site is to turn off .sigs, and to use the new-style commenting to adjust my comment thresholds. I have threads which are not highly-modded show up as just a "X comments here" note. Generally even if something is downmodded for being unpopular it will still get a lot of replies, so you can use the to keep an eye out for downmodded but still worthwhile posts. The Slashdotter Firefox extension is helpful too.

I don't really have an answer to the 'early posts are more important' problem though. That's been bugging me too.