How is R&D mode like jailbreaking? The flasher is provided by Nokia and the functionality is documented. You don't need R&D mode normally to get root access, it's only needed in that obscure usecase you're bringing up.
How is using an exploit that google is trying to stop the same as installing an app that is perfectly legally for download in the extras repository provided by Nokia.

You have 100% control over the device, save some drivers as far as I can remember and some crappy built-in apps that are easily replaced with FOSS solutions.

On maemo 6 there will be a drm-mode, but it will be perfectly optional and the device will be 100% functional if you don't want to listen to drm media or install drm apps.

You can't get more free and in control than that. Maybe only if you build the device yourself.