what happens to NSLog info when running on a device? Where does the text go? Does it get saved? Is it therefore a big overhead when running on a device, or does it effectively get sent to null?
Since Xcode 6 the device manager pane has been split into its own window. (Window > Devices, or Command-Shift-2.)
Once there, select your device, then show its log by clicking the disclosure triangle at the bottom of the window to the right of the sidebar.