I have my NEX 5N before the purchase of my K-5. And I have K20D and K7 when I get NEX 5N. It is the best traveling camera that I have gotten. I used to like my past K-x for traveling light, but my NEX 5N is up a couple of notches in terms of size, lightweight and good high ISO performance.
To be honest, I think you can do just as well if you venture into Fuji, Olympus or Panasonic. They all do have a MILC that is well suited for traveling light.
As for the NEX, it is lacking flash, I recently get
Wansen Hot-Shoe adapter for NEX
and you can visit my blog page for reference as I used my NEX5N with an external flash and Cactus v5. I have to use flash in manual mode. I have many articles in my blog posts and
flickr stream mixing between my K-5 and NEX 5N. Both are used in my hobby and I will not dump one over the other as they both serve me good. In traveling light, my NEX is my go-to camera.
[update:] If you consider the NEX and that if you can afford it, go with NEX 6 or NEX 7. Both come with an EVF which is missing in the 5N.
Thanks,
Hin