the rns-e is a quality addition to your car mate, it finishes the dash off a treat, the intergration is spot on, as you say, the bluetooth will intergrate too, as for the bose, shouldnt be much difference.
having it intergrate with the dis on the dash is also very handy.
as for the navigation system itself, its not the most upto date system but is more than ample, the only bugbare i and others have is that its not full postcode entry, but to be honest once your used to it its fine, if you have a multi function wheel then you can do the sds hack, which allows voice commands to the rns-e which is another plus for having one.
i dont remember ever reading that anyone isnt happy with the rns-e and that there taking it out and selling it, once youve got it im sure youd be more than happy.