Love my NEX-7 + SEL 50mm 1.8 for portraits. Rented the 10-18 for my Summer vacation; overall liked the lens with one caveat. At 10mm the corners show smearing when shooting at f/4. Mostly clear up at 12mm or if you stop down.
I'll keep that in mind, I almost added the 18-105/4 PZ lens, but declined.
I'm kinda going in the reverse direction of logic, lol. Full frame is better as shooting wide, yet I can see myself using the A6000 with 10-18 as an ultrawide specialty on vacations -- because it should be so small and easy to carry. And much rather bring that combo to a beach than my D750. Plus, I'm not thrilled with any of the telephoto lenses available for the A6000... at least not that would also save me in size. But ultrawide, I usually shoot at F8 anyway, so I don't need a big fast lens.
I was strongly considering getting an APS-C Nikon, like the D5500 to serve as my backup. Would have been nice to have full lens compatibility with my Nikon glass collection that I've built up nicely over the last year. And that would have given me some real options for extending my telephoto use -- My 300/4 would have become a fully usable 450/4 on the D5500, and a full 630/5.6 with teleconverter. With current adapters on the A6000, the lens won't have AF, it won't have any way to control the aperture (it's electronic aperture, so an aperture ring won't work), and from what I understand, the lens's own VR won't work. The new commlite adapter may make it more usable, we will see.
But then I was swayed by the small size of the A6000 when used with small APS-C lenses. If I simply stuck my big full frame lenses on the Nikon D5500, I wouldn't be getting much of a size savings. If I bought all new APS-C lenses for the Nikon D5500.. then I'm buying new lenses anyway, and the set-up isn't as small or good as the A6000.
So my plan:
For my professional portrait work, sticking with my Nikon D750, but the A6000 with 50/1.8 as a backup portrait camera.
For vacations, bring both cameras, but carry based on my needs: Going to Disney World/Magic Kingdom, for example, use the D750 + 45/1.8 for dark rides and people pictures. A6000+10-18 for landscapes. So carrying 2 cameras and 2 lenses. But about the same overall weight as carrying the D750 with 2 lenses, and no need to change lenses.
For a vacation such as upcoming cruise, use the A6000 almost exclusively when off the ship, so as not to be carrying around much weight, nor thousands of dollars worth of gear.
I suspect that just with the 10-18 and the 50/1.8, I can cover the types of shooting I'd want to do with the A6000. Obviously, those limited focal lengths won't make it a full time camera for me. But should be useful. And I'm getting a decent price. I'm kinda curious to try eye-AF for portraits on the A6000.