They have been the subject of some past discussion, and reviews that cover most possibilities...
The overbearing memory I have, of buyers' comments posted here, were inconsistency in delivery times. Some things were perfectly quick, other times people bid on a motor only to find out it was weeks from delivery. (However, sellers here might say the same thing about others delivering on time!)
To some extent, all these sales are caveat emptor - if you don't understand something the seller says, ask them. If you can't accept the rersponse, don't buy it.