We all want wonderful experiences as users. The crux is almost a question of "how we want things to be" and "how we want to get there".
For me, the 100% JS MV movement is wonderful for a specific genre of app: An app that is:
* Behind an intranet
* Behind a paywall
* Behind a login-wall
* Prototypes / Demos / PoCs / etc.
But for the open web -- wikipedia, blogs, discussion forums, journalism (etc.) this movement detracts from the web as a whole, in that it excuses developers from having to worry about degraded and/or non-human consumption of their websites' data.
We have to ask ourselves what we, as humanity, want from the web. Do we really want a web of 100% bespoke JavaScript MV web-apps with no publicly consumable APIs nor semantic representations? If that is the intent and desire of the developers, designers and otherwise educated-concerned web-goers, then fine, let's do that and hope it works out okay...
But there is an alternative that has its roots already planted deep in the web -- the idea and virtue of a web where you can:
* Request an HTTP resource and get back a meaningful and semantically enriched representation
* Access and mash-up each-others' data, so as to better further understanding & enlightenment
* Equally access data and insight via any medium, the latest Chrome or the oldest Nokia
So, please, go ahead and create a 100% JS front-end but, if you are creating something for the open web, consider exposing alternative representations for degraded/non-human consumption. It doesn't have to be progressively enhanced.
Imagine for a moment if Wikipedia was one massive Ember App... And no, Wikipedia is not an exception from the norm -- it is the embodiment of the open web.