Harmattan is a very nice UI with some innovative features. But if underneath it, loading software will require chasing down "dependencies," then maybe the beauty is only skin deep.
N770 was understood and loved by the hackers, but not by the general public, and was a commercial failure. It was also more powerful than most of the other devices out there and ran more general purpose software than the popular PDAs and smart phones. (WM could run CE apps but not Windows apps, N770 could run any X application with recompilation.)
It wasn't until the iPhone that a Unix device was accepted by the general public, and only because Apple did a better job of hiding that from the public. (And other things as well