Amazing. Default Folder X has “secret settings” that allow you to jump to the recently used folders in the Finder. By turning on the two settings pictured, you can use option-up and option-down to instantly jump between recently used folders (the OpenInFrontFinderWindow isn’t strictly necessary for this, but prevents a new window from opening every time).
You can reach this dialog by option-clicking “Settings…” in the Default Folder system preference pane.
Read more about the settings on the St Clair software blog here.
