I have sold over 5 books on half.com and the response has been immediate. I am also a regular buyer of books on half.com and the service is excellent.
On half.com u are assured of the quality of the book and also the condition it is in, ebay.com doesn’t guarantee the quality of the item sold.The only downside according to me for half.com is that the price u quote for the item will not go up and u will get what u quoted if u sell the item on the other hand with ebay ur quoted price could be exceeded and u can land up getting more than u quoted if there is a demand for the item u are selling.
Since half.com makes a direct money transfer into ur a/c u are assured of the money for ur sold item on ebay the buyer may not respond and u are left paying the fee for listing the item.