Feel free to try them out, and let me know below if you have any issues, and on which browser you're running. (Would be nice to fix any weirdness before Scala-2.10-M4).
Available Keyboard Shortcuts
Browse Scaladoc with arrow keys. Search for something in the left side bar, hit the down arrow. Use the up/down arrow keys to move to packages/objects/classes/traits, and hit Enter to load the corresponding page in the right panel.
Toggle between panes with tab key Hitting the tab key will toggle between the text filter in the left pane, and the text filter in the right pane.
Up arrow key overrides auto-focus in right pane When the right pane's text filter is selected (and the input panel annoyingly sticks to the top of the page), pressing the up arrow will automatically scroll to the top. Nice when you want to read the API comments.
Escape resets filters (oldie but goodie.)
Page up/down only works without text filter selected in Firefox. Though it works perfectly well with or without the text filter selected in Chrome and Safari. No clue about IE (no access to a Windows box). Will fix shortly.