Hah, that's funny. "PS2" works to register at Geekhack? How vintage.
I tried "DIN" first >.>;; It *seemed* like the obvious answer =(
PS2 wasn't working for me either when I registered =(
the code makes the naga $56. there goes my afternoon, time to start reading reviews.
If you do anything that benefits from a lot of extra mappings being available, get one. If you can get used to using them, they're amazing. I really prefer the old MS Intellimouse (rip V1 and multiple V3s) shape to the Naga's, but it's also not as bad as most of Razer's mice (it's not that awful--to me--"adder" shape). I personally don't usually use more than 2 and maybe 3 rows (going... vertically) of the side number keys, and that's still so nice to have. The side mouse buttons are a little awkward, but I don't really have trouble hitting them personally. Mine's been used for easily 1000+ hours of gaming, with the side keys used in the main "rotation" for playing WoW (so basically 1 press per second while playing), and I've had 0 issues... the black coating on the side keys is fading on the 7-9 and 10-12 row along the edges of the keys nearest me (so there are some lines of light leaking through), that's it.
Be aware that the default "num pad" mode is *actually* a numpad (even affected by numlock), so all of the usual concerns of modifier keys along with num pad keys apply ("Why doesn't shift+5 do anything!?" etc). The software now allows full remapping (and even macros) of the side keys, though. And 1-2-3 mod works fine of course.
There, there's a mini review, if the negatives don't bother you and you were at all thinking of buying one, go buy it =P