Rather than the 2-pane approach, and a separate setup interface we used to have, we've gone for a single pane device list, as you've probably seen on your smartphone.
We also do away with the "Discoverable" switch (your computer will be visible when this panel is opened, invisible if not), and nearby devices will show up at the bottom of the list. Simply click on one to set it up.
Clicking on an already setup device will bring up the properties, allowing you to connect to the device if necessary, or link to related preferences.
Finally, the biggest part of the work was making sure that the new setup mechanism worked at least as well as the stand-alone wizard. This means that I got 17 of my most representative devices out, and set up every single one of them. Edge case.
There's a good chance that we'll make some additional, minor, adjustments to the wording, spacing and behaviour of this panel before the GNOME 3.12 release. I'd particularly like to make clicking on a device connect to it if already setup and offer some other way of accessing properties.