I want to vote for 3 options: the open-source community, techies, and mobile device "power users". Mass market, not yet. Maybe in later stage though. Reason: platform too young (in the 5.0 sense), software must adapt (to compete with other platforms), price too high (in that sense iPhone or Palm Pre are not for 'mass market' either; we need more Maemo devices for different target groups ).

No way everyone is thinking that. Heck, there is also still a market for non-touchscreen phones. Each have their place. More important question is: how much market place. Now that is difficult to answer.

Current soft keyboards have advantage of easily remapping. OLED based hardware keyboards have this advantage too, but are too expensive, and the number of keys is still static. I can see these initially being used for hot-keys (like home/email/contacts/agenda), but otherwise... price, for now.

That is one disadvantage of hardware keyboard: localisation. Inflexible to change during usage with change reflecting and lowers reselling value while inflexible to buy from other countries due to hardware keyboard (unless user not care). Now, afaik you could change the hardware keyboard of N810. At least you can with many laptops. But I don't know about N900...?

Why I like hardware keyboard: I like to feel my keyboard, feel the hardware keys. I like the tactic feedback of a hardware keyboard (especially the old IBM keyboards). I like that a hardware keyboard is static, it never overlaps the screen changing the usable resolution of the screen. The screen doesn't become dirty either from typing. The number of mistakes made during typing is considerably smaller than on touchscreen (yes, I do compare with my iPod touch).