I find the Zaurus C-1000/3x00 d-pad preferable to the N800 d-pad. On the n800, it's difficult to avoid pressing the center button when moving between two directions. Also, it's difficult for me to press with the pad of my thumb, forcing me to resort to using my fingernail. Diagonals are difficult as well. Also, it seems to have some issue with auto-repeating, even on short key presses. I'm not sure if this is hardware or software. Really, I find it sub-optimal for almost all uses, not just games. Now that Sharp discontinued the Zaurus, I recommend Nokia should pick up a second-hand C1000 and rip-off the d-pad design wholesale. (Slightly kidding in that last bit, but it would be a big improvement.)

Some suggestions to Nokia:
+ shaped or o shaped d-pad instead of square.
Recess the center button slightly so that it is even with the direction buttons, or even deeper.
Reduce effort to press, while also giving more tactile feedback.

-John