The empirical scientific proof that fixing defects first would be the way forward is here for me:

Since I have returned from a 2 week trip during which I have boldly volunteered to trial the Jolla as main phone after having upgraded to upgrade 10 I have dumped it in a drawer and taken the N900 as main phone with a feeling of relief.
I did not have such feeling when using the Symbian 808 for prolonged periods.

Jolla plus:

-battery life still very good for my usage pattern

-using it as a mini tablet for reading eBooks via FBReader gave me great pleasure. Also the minimum brightness is not too harsh on the eye.

-survived already 3 - 4 drops on hard tile from about 50cm height. Frame so far has absorbed shocks and glass not yet broken.
Now most of the corners of my Jolla are sexy round instead of straight and if I aim over the Jolla its now somewhat curved as well, but not in the width like an LG, only in the length like iPhone 6 max! Anyway, its holding out so far.

-excellent virtual keyboard for basic typing such as replying SMS. I experience performance and feel empowered by the Jolla.
Space bar is a little short resulting in a lot of "." in between words instead of spaces.



Negative:

-New "feature" applications closing themselves (what were they thinking - what would have been broken on the long term if this "fix" had not been applied - who tested and approved this feature - incompetency peeking)

-Several bugs (unable to connect to Wifi of choice certainly one of the most annoying N900: online as it happens, Jolla: online if it happens)

-inserting a new SIM card -> something looking like native Sailfish app gets installed w/o further notification or my permission? I don't want that to happen the way it did.
See screenshot: "maxSim". It contains crap links by network provider Vinaphone. Need to check later if this is Android or Sailfish native.



-Struggling with interface. auto rotation of camera interface, feeling uncertain when filling in forms on websites, saving passwords or not - which direction to swipe..
Maybe I did not use the device frequently enough until now but I feel no blind automatism coming up. Instead I find myself uselessly swiping in circles and have to think more before acting remember stuff like was it left or right to prevent work being lost.