To date I have bought 116 old and new kits and promos off US ebay with three mildly problematic transactions:
a) A sealed 1964 Cadillac - but the parts were nearly all off the trees. Can happen but I'm still wondering if it had been re-sealed.
B - A 1959 El Camino sent in an envelope - box got crushed a bit. My fault because I didn't notice the seller had said at auction he would sent it like that.
c) A Camaro promo in decidedly worse condition than the auction photo and description. The seller had sent the wrong one and resolved the issue by paying return postage and sending me the right one. We all make mistakes and I actually felt sorry for him - instead of a small profit he had a substantial loss.
All but 2 packages were sent without insurance, all were well packaged (except the El Camino) and arrived within a reasonable time frame.
My latest purchase, an X-EL 59 Chrysler was sent to my brother's NJ beach-front house. (Many US sellers won't send overseas.) He had to abandon the house before he could post it on as Sandy rolled in. He sent photos today and the bottom floor is severely damaged, the entire contents washed away. He tells me the model is on the second floor so there's still hope I'll get it one day. Of course he has other concerns right now.