I'm not to sure on the rest of you but I havn't been to levels 5-9 in ages. Mainly because of the lack of quests in those areas.
Some quests down there would be great and would flesh out those areas.
I say at least a minor quest (fedex quest even) per level would allow people to want to explore more levels.
I say the server was at its most packed with the proving grounds were opened. A new level always brings people back and its has been a while since the last new level (We know this is because of the HUGE work you have been doing on waterdeep and we are all eagerly awaiting the next 4 parts of this update)
I might go do some marketing for us on the Bioware boards