The proper way to do it in my opinion is:
U : Home
I : Up
O : Page Up
J : Left
L : Right
M : End
, : Down
. : Page Down
For the Ins and Del keys, I'm flexible, but H and N seem logical.
The above mapping means my fingers can very easily use those keys while my hand stays on the home row, and with the exception of the Ins/Del, my fingers are in basically the same position as they'd be when using the numpad cursor cluster.
As you said, everyone has a different opinion. I never learned to use the cursor/editing keys of the PC's numeric keypad; my major PC use came after the advent of the separate cursor keys and editing keypad, so those are what I learned to use.
For that reason, the keypad I mapped onto my Siig MiniTouch's keypad keeps the inverted-T cursor key arrangement and goes as follows:
U: Home I: Up____ O: End_ P: PgUp
__J: Left K: Down_ L: Right_ ;: PgDn
___M: Ins__ <: ---- >: Del___ ?: ----
Also, the additional function key(s) needs to make multiple-modifier uses of the editing keys easy. For example, I'm always using Ctrl-Delete to delete the next word of a line. With the editing keys buried in the alpha keys, you need to be able hit both the control and the function keys easily - but it's an awkward reach on the HHKB (far left + top right + bottom right keys). The same goes for using control and a cursor key. I think the HHKB layout would be improved with an additional Fn key on the left, like on the HHKB Lite 2.
That's my .02 cents worth.
-- Bill
