Keyboard shortcuts
The shortcuts derp adds on top of Firefox's, and how to change them.
derp's own keys
The chrome controls sit on Alt+Cmd (Ctrl+Alt on Windows and Linux) rather than bare keys, so they cannot fire while you are typing into a page.
Alt+Cmd+A hides or shows the address bar. Alt+Cmd+S hides or shows the panel sidebar. Alt+Cmd+Z toggles zen mode. Holding Alt+Cmd and dragging moves the window from anywhere on it, with no title bar needed.
Navigating without an address bar
Double-click a tab and it opens into a text field: type a URL, press Enter to go, Escape to back out. Tabs in a stack's second row behave the same way. With the address bar hidden this is how you navigate.
Back and forward stay on Cmd+Left and Cmd+Right, as in Firefox; Cmd+[ and Cmd+] work too.
Changing shortcuts
derp's shortcuts are listed and editable in the Hub, alongside Firefox's own. Conflicts are flagged as you assign them.