Many of the comments are reminiscent of comments on the LGW thread when Norwegian announced a new LGW base in early 2103, won't work, not known, unknown brand, Aer Lingus tried it failed and so on.
Edinburgh is of course a much smaller airport and catchment area, but the evidence so far with Norwegian long haul is that it grows the market off the back of a lower price, people in Scotland my flinch at the thought of 6+ hours in a 738, but this common in many areas of Europe, it will also help with connecting traffic, the Norwegian CEO claims up to 1 in 3 passenger on Norwegians US flights are connecting through Norwegians services in to LGW of which there are over 500 a week now.
The key especially with smaller aircraft is airport access costs and slots, the drive distances people will accept in the US are longer than here, most roads outside of major cities in the US are very quiet compared with, time is the question how long does it take to get from Leith to EDI airport? by car?
Norwegian are currently flying out of Milwaukee to Mexico and Jamaica as well as the French Caribbean to Boston and JFK with the 738
They will do the bucket and spades routes on the NG but with Spanish based aircraft the more passenger use the product so they will return the proof of that is at LGW where they are now number 3 behind EasyJet & BA, by years end Norwegian will have 21 787's in fleet.