The shared library leads to my big issue with the NX. I'm almost definitely going to get an NX, but it might end up just being the portable one. I'm not seeing an extensive reason to double-dip in this scenario.
If the console is just the NX Portable game in 1080p/60FPS with bells and whistles like antialiasing and anisotropic filtering and all that other good stuff, I think that the handheld-only route becomes very viable.
I'd probably buy the console and give the handheld a miss. You may think that's Nintendo loses out in system sales but they will make money in software that would be ported to both systems. I have not bought a 3DS or a Wii U as I feel there isn't enough games on each system for me to justify a purchase. Instead I play the gamed I like on my brothers systems. However if the Wii U could play the entire 3DS library I probably would have bought one.