I've bought a lot of stuff from Ebay over the years and the very few problems I've had have been very minor. I'm usually pretty careful to only buy things I can return if there are problems. That makes it pretty safe.
Actually the worse problem I had was when what was supposed to be a Kobo Glo turned out to be a Kobo Mini. It was priced really cheap even for a Mini so I probably would have kept it in any case to share with a neighbor. In fact I didn't have to decide that because I emailed the seller and he told me to keep it and he'd already refunded my money as soon as he got my email. I'm fine with problems like that.
Barry