I have bought a few things - and have even bought and sold guitars, which I would never have believed before. I actually got onto eBay the first time to buy a guitar and it went well. They are so personal and depend so much of the feel. I ended up making sure I exchanged a few emails with the seller to see if they knew what they had and were players, so could describe it in terms that would help me understand the guitar’s playability. I have actually fared quite well sticking to this approach - if the seller doesn’t respond or doesn’t know the answer, then even if the guitar looks really great, I don’t pursue it.
I have also bought electronics and clothes - so far without complaint.