the Sony Alpha DSLR focus really well in video mode, it is just the same as focusing in photo mode, becoz of their translucent mirrior, so they are able to use Phase Detection AF all the time.
the down side is, aperture has to be wide open, but if you want full control, you lose continuous AF, so not both....
The 5n is great, AF is quicker than the original NEX3 or 5, but still slower than EP3, GF3, and the EM-5. but IQ wise, i am very satisfied with it. For travelling, you can get the 18-200, both Tamron and Sony made one.
if you want it for portrait, there is only 1 lens available if you want bokeh, the 50 F1.8, but it focus even slower than the kit lens, don't know why.....
wait for another month or so, Sonyalpharumors mentioned the NEX 5n successor will come soon, so the 5n price will go down