Well... R and L!! Just kidding, it could be Fn and Ctrl, like in the N900, but if they are done like shoulder buttons.... OMG, the gaming goodness! This would be a dream, really.

Offtopic: gaming

I have actually been thinking about a gamepad possibility lately, and one of the "problems" is the design, specifically how to implement shoulder buttons (and some kind of analog input, now that we mention it) inside an OH. What shape would the buttons have? Do they pivot? Where? How long should the button press go? Taking ideas from Xperia Play...

Now, continuing this line of thought: as I understand from what I've read about how the trackball and the hall sensors work, these trackballs are analog, or at least have different steps so a "semi-analog" (ok, "digital progressive") movement could be extracted (like when d-pads are mapped to either neutral position or max values of a virtual analog joystick). The Jolla is rather big, so the question is now, if there are shoulder buttons, could there also be 2 trackballs in order for this to be an all-around keyboard and light gaming OH? Incidentally, this would also solve any right- or left-handed issues we would have.

Edit: Ok, seems it took too long to write, and you yourself beat me to the Xperia Play reference. Which is in fact nice