I would like to see the sub-categories 'Used' and 'Unused' removed and replaced by a radio button on the Selling Form with at least the following conditions selectable:-
Mint never hinged
Cancelled to order
Very fine used
The Stamp Condition should be displayed as part of the description.
Along with this we would need a filter on Stamp Condition.
The big advantage here is there would be far less maintenance needed for including Used and Unused as sub-categories. Also, these sub-categories are currently not available for all countries, which is a huge anomaly.
As a programmer I believe this would be reasonably simple to implement.
I also think that filtering on Stamp Condition to this level (ebay only provides new and used) will be a big advantage over all of the alternate auction sites.
(This is also posted on the Categories and Philately threads).