Selling: Fortunately no issues in probably 75-100 sales.

Buying:
I had to wait once a long while to get a new DA hub from a HK based seller. Filed w/Paypal and all that, then it magically showed up 2 days before whatever 90 day deadline the seller was up against. I figure he was just out of stock and waited to collect enough orders to replenish.

Two buying situations were with two brick & mortar bike shops.
1. I bought a NIB Shimano UN72 BB. Should be pretty simple, huh? I don't even remember now what length I wanted, but they shipped me a different length - one that did correspond to the Shimano stock number on the box, but not what they advertised. When I asked about the discrepency, they claimed I didn't know how to measure the length, nor could I interpret the number on the side of the box. They finally agreed that would take it back at my cost to return, less what I paid for shipping. Because they shipped me the correct item. Sure. I slammed them with negative feedback on the last day @ 11:45 PST(no retaliation) and kept the BB for some future use.

2. The other was a purchase of a Phil fixed/fixed hub. It came with two DA cogs and lockrings, extra bearings. All pictured together. (What a fool am I). Sounded like a great deal so I bid and won. The description failed to mention that the spokes had been cut off and the cogs had been ridden onto the hub, and hard. I had to partially build a sacrificial wheel (junk rim, old spokes) to twist the cogs loose. I just wouldn't have expected this treatment from a bike shop. I had purchased something from them in the past, and it too had something conveniently left off the description, but not as bad. I'm wary now in bidding on items from this particular "reputable' bike store.