I have always received my cards quick, but I am just down the road from them too. Not sure about haphazardous. Mine always come packaged securely. I usually do end up getting 15-20+ cards at a time, but that is just my buying habit more than anything. I visit the site and then maybe don't go back for a few months. The S/H cost is the biggest deterrent to buying more.
I have noticed the underbidding that someone mentioned. Unless I am buying a serialized card, I usually go with the lowest price, even if it's just a penny, because why would you purposefully pay more? You are buying from specific sellers, but in a way, are not. The service you get is from COMC, not the individual sellers. I suppose if you bought a bunch from the same seller, you might want to give them a few cents more on a card some other seller has slightly cheaper, but it couldn't be much more. I don't know if the sellers even get to know who bought the cards from them? Anyone know?
I have not been able to try the offer function, because I can't get credit loaded (due to my previous issue - TAXING OF MY CREDIT PAYMENT). If sellers are generally willing to bargain a little, even better. For now, I just buy what I think is priced fair and pay full price.