I reckon that in the grand scheme of things, this may be quite tiny, but if you put in context that Jolla is a small company (is it the smallest that is doing a device+OS?), 50k devices booked is very good news for them - if it is true that they need to sell 100k devices, having booked half of that even before the device is actually out is very encouraging for them as a business.

The key thing that I take away is: they are likely to have a decent lifetime as a company, hence more devices will come, and support will exist for anything they produce. Obvious questions are quality, etc., but we'll have to see. The competition isn't very good at post-sale support, so it isn't like they have to match very high standards.