Well, all these things are no problem at even with very outdated hardware as quite a few people run SSH servers, FTP or GIT repositories on their home routers, that are much less powerful that even the N900, without any issues.

A proper GUI toolkit (Qt,EFL,..) integration (location, camera support, video playback, 3D) might be a bit more difficult to get going.

I think the issue is probably that the manufacturers don't see "us" (power-users/developers) as the target group for their devices so they don't bother to officially support all this.

On the other hand, who would like to develop applications for such a limited, locked down and everyday-unusable device (case in point - Windows Phone)? Not counting commercial developers of course.