The Verge's reviewer didn't like it. I have yet to get my hands on one. It is strongly a "global gestures" UI. Some people like that as a way of enforcing consistency. That will have some possibly confusing effects on Android apps running in Myriad's compatibility environment. Also, the last time I looked at Myriad's technology, they were using their own Java VM, which means, at least,some kind of Dalvik to Java byte…
The Jolla UI looks and behaves similar to the Blackberry 10 OS, which is a good thing, and an improvement on Android and iOS. I have a Blackberry Z30[1] and I don't think I could go back to the "old way" of using a smartphone. BB 10 feels like a true smartphone experience, as subjective as that is. [1] http://ca.blackberry.com/smartphones/blackberry-z30.html
A non-discoverable interface on a device this late to the party is not going to be good for market-share.