* Main problem was complete network dropouts / restarts (only used it for 1.5 days, three strikes and you are out, reliable is critical in small office).
* 5GHz simply not usable (Of 4 devices I tested with 5G, only one seemed to work at all. Macbook, Toshiba laptop connected but had problems. Nexus Galaxy from UK couldn't see WRT although it can see a 5G TimeCapsule). It is only using bands 36,40,44,48 (Odd or not? I could see nothing that indicated what country the bands were set up for).
* linksyssmartwifi setup that wants you to be connected to the internet for the initial set up of the router. Mind bogglingly stupid wants you to set up an account with linksys as default! (PS: if you don't use the smart setup, then the admin password is admin).
Was trying to use it for a small office - specs imply it should be able to handle 10s of devices - maybe I was being optimistic! Will look at getting something to handle more devices that is more reliable.
Background: Bought WRT1900AC at Noel Leeming so it should be NZ configured (30% off - $265). Bought it to replace router that glitched about once a month (Netgear N600 - horrid glitch: random unobvious side-effects elsewhere, making odd troubles until router reset, arrrgh).