In fact no problems with anything I've bought and only two problems with items I've sold.
Both selling problems were with cell phones. The first one was several years ago when I sold a cell phone and the buyer thought I should have included a charger. The auction listing didn't say I was selling a charger with the phone but he assumed the phone would come with a charger. We eventually worked that out.
The most recent experience was selling an iPhone. What a fiasco...
The buyer sent me an email several minutes after winning the auction asking if I would wait 2 weeks until he got paid for him to pay for the item he won. That's very unusual in my experience since auctions - online or in person, only work on an immediate payment basis. Imagine how poorly an auction would work if you could bid on items you couldn't pay for.
Over the course of the next two weeks I exchanged many emails with the buyer answering questions he had about the phone. It's wasn't a good idea on his part to wait until after he won the auction to ask questions but I did my best to answer him.
He eventually sent money to PayPal but they aren't releasing the funds to me for up to 21 days "as long as the buyer doesn't report a problem".
That seems crazy to me. He's had the phone for over a week now and actually replied to my email saying he wanted to keep it for a week to see how it works. I have no way of knowing that he might drop the phone on the sidewalk or into the tub...or just decide it wasn't really what he wanted after all. The phone worked fine when I shipped it. I didn't offer any warranty and stated in the listing that I don't accept returns.
PayPal has a different policy.
I need to replace my iPhone in the not to distant future since a portion of the touch screen is failing making it challenging to dial numbers and perform other functions (like listening to voice mail). That should be another eBay/PayPal adventure when I sell that thing.
Since I'm in the market for a new phone, I'm debating if I should violate my "don't buy stuff at Wal-Mart policy" to take advantage of their $97 iPhone 3G S offer. Probably not.
I think I'll wait to see what the next gen iPhone has to offer and continue to limp along with my 2 year old 3G with the failing screen.