I voted for:
Fix the migration process (the Windows menu and wallets with a large number of private keys)
Fix all the known bugs in the GUI
Make the affiliate program practically work (i.e. without the need to run a separate server)
Upgrade the market page to a Poloniex standard
Tidy up the look and feel of the GUI (font size, colors, replace error messages with user-friendly texts etc)
So basically bug fixing and making the GUI better to make the best user experience possible, that's what ultimately will bring more people into BitShares. I think those should be the priorities right now.
Then once we have something that is working at 100% and appeals to everyone, we can start on expanding, adding new features, etc