There are some things I think Jolla does very well.

Working with upstream projects in collaboration with other stakeholders is generally a pretty good example of that. We've seen a pretty good track record with ofono (+ Ubuntu Touch), Qt (+ Qt Project), and a bunch of other projects.

I also think Jolla do a reasonable (if not great) job at communicating upcoming software progress, considering how frequent releases are: changes are always visible in the repositories, a view into the next update's changes is generally available before it comes (still a relatively new development and not a perfect one), larger technical announcements are sometimes made if there's any hint of problem or interest. And there's changelogs with a fair amount of detail at release time.

But there's also things that I think could be done better.

In particular, I think things like a public platform SDK (similar to what is generally used internally for development at the OS level) could be helpful.

I'd also like to see some work done on making a more cohesive OS development environment (software is available from a spatter of repositories all over the place, often with incredibly blurry lines about what goes where - sometimes to the point of being completely arbitrary) and so on and so forth...