Thanks for the post Q.
A great example is mini-map rotation.
Everyone has a personal preference for this - north up or avatar nose direction up. That preference is deeply rooted in our own perceptual systems, to the point where a nose up person may think nobody could possibly use north up and vice versa.
I started out in SL as a north up person, and was continually infuriated at having to turn off mini map rotation every time I installed a new viewer or had to discard preferences.
Then I discovered that during boat racing, you have to see the boats that are behind you in order to avoid turning across their path. This is easily done with the minimap rotating, and not so easily done with north up:
Same user, new use case = new preference.Meanwhile the rotation control migrated around the user interface. However, the further it is from the point of use, the less likely it is to be found and used.
It's now (V2 at least) accessible from a right mouse click in the mini map. Now I can set it dynamically according to what I'm doing - It's no longer a preference, it's a useful tool.
Put control at point of use = less interaction burden + more discoverable = more likely to be used.Re complaints about screen real estate - we're going to have dockable tabs soon, let's hope this solves that issue.
But that leaves the people who declare that the UI is unusable or worse, and the only reason they can give is that it's dark. Could we please just have an original colors skin option, so we can separate the structural issues from the cosmetics.