At my current job (gov. agency) we use this internal tool - think marine traffic combined with flightradar24 - and it is great. Truly awesome.
It's been developed for almost 10 years now, by a relatively large consulting firm.
But I believe a large part of the success comes down to the following:
- The core dev. team is still mostly the same. When you think about it, 8-10 years is pretty much an eternity in the world of software development, so it's pretty incredible that they've managed to retain so many members.
- Development cycles are very fast, and communication between end-user (us) and the product manager is very good. There's very little red-tape or committees between us.
With that said - even though the product is quite extensive, the number of users is quite small, only around 500 active. And they are all gov. workers, though in different departments.
On the other hand, I've also seen some dogshit products in the wild. Usually in the scale has been much, much larger - and the budgets, too.
Observations from those have been pretty much the inverse of the one I mentioned above. Huge, huge teams - always new people. Insane turnover. Getting new features takes years, and everything goes through multiple levels of bureaucracy. By the time something has been implemented, interest has changed.