I have a few things on my wish list...
1. A tray application (an app that resides on the system tray) that notifies you that you have games waiting. I'm a programmer by hobby so I may do that myself.
2. The PGN/FEN in the same window as the game itsself. So I wont have to go back to the game list and click on info. Sometimes I dont remember what my last move was and I have to go back and look (Maybe thats why I'm such a crappy player).
Even if the tray app is only available to subscribers... that may intice more people to subscribe to the site.