re a 11-42t 11 speed cassette, although I do like cassettes with closer ratios, it is clear that compared to a 11-34 9 speed cassette that I have toured a lot on, and to a 11-36 10 speed cassette on my wifes bike---the % jumps on the 11-42 11 speed are very very similar--so in real life, the jumps are perfectly acceptable to use.
sure, if I was going to set up a 11 spd bike for touring at some point, I would prefer to use a double and use a closer cassette, just cuz its nice when you have closer jumps.
I still feel though that increased chain line and therefore less longevity to drivetrains HAVE to be an issue or factor over the long term, and as mentioned, for touring and easy paced riding, shifting fd's is by no means a hardship or have any downside. Racing mountain biking or cyclocross is one thing, but for all of us doing touring and such, a single chainring really doesnt have any advantages at all compared to the positives.
and yes, I still figure the "one-by" thing is great for manufacturers as they can crank out more parts for more bikes, therefore more profit.