Always better to make specific quests/suggestions than just saying "x sucks, please fix it".
Features needed on the GTN:
add the ability use search terms, without needing to select a category first separate moddable (orange) gear from from blue gear in the filter add the capability to search for armor for a specific slot (head, feet, etc.) add the ability to filter for a spefic stat type (cunning, willpower, etc.) retain the "quality" level searched between searches retain the last price you posted for the same item when creating new postings
That's all I can think of at this moment.
-edit-
Updated list.