Well, then white and light blue for special characters, on black keys.

I've owned both keyboards with these colours and keyboards with yellowish/gold on black, and my preference is clear.

Most of all, we need a quiet keyboard. The N900 keyboard is silent and at the same time has a great tactile feedback. I used lots of other keyboards and none had the same feeling, that's a shame. It's really important in my opinion.

Finally, several localized hardware layouts, not only software. I know Scandinavian and English are planned, but I hope AZERTY will be available too, for the keyboard to be really useful (for me) considering its likely price.