Honestly the best used stuff I've gotten has been from shopgoodwill. As you say either in the "40" packs, smaller lots, or individual records. Rarely gotten skunked on an unplayable record. By comparison Ebay is a crap shoot. Local secondhand places (antique malls around here have some really amazing sellers...and some yahoos) haven't proven as consistent as shopgoodwill! We do have Mad City Music, which is an outstanding record store (selection, price, condition, atmostphere, customer service...hands down the best place in the area IMHO).
That said...I'm starting to stretch the bounds of what's availble selection wise of shopgoodwill. I built 80% of my Hafler/Pioneer S-710 system from shopgoodwill. So no hate! But I've reached that point where the 40 pack or records are stuff I'm not interested in or already have for maybe 1-3 records I actually do kind of want. Still, it's a great entry point to the hobby of record collecting!