The problem with "rich user experience" is that there are so many of them.
From the audio player app with graceful curves instead of square corners, the circle/bar (poweroff symbol) somewhere instead of "X" in the corner to close, shelves that open when you hover over a specific part of the app... you have to learn a new way of doing things, and it's only for that one app.
Download images from a camera or phone, but it doesn't identify as a "disk", it requires an install disk so that it appears as a separate something in the disk listing, at the end, with a different icon. With no "plus sign to open". And I can copy images from camera to disk, I can delete images from camera, but I can't "cut/paste" images from camera to disk.
The original "Mac Paint" was awesome because the icons represented what the program actually did. Flood fill was a paint can spilling paint, select (the icon) looked like the selection box, and so on. Now everyone uses different icons to mean the same things.
"Customize and control" is three horizontal bars (Chrome), or a gear-like thingy (GMail) a little arrow (Facebook) or a sometimes a wrench. It's not hidden under a menu any more, because customization is something we need to do frequently, of course. And menus are out of style, no more pesky named categories of things you might want to do.
Whenever a new app is installed, the user has to spend time rummaging around the system figuring out where everything is, and they have to do this for every application. There can be no muscle memory, and little or no reliance on previous experience.
(For a particularly awful user experience, install Anki sometime. And then try to work with it.)
The solution to every problem is to google "how do I do $action in $application", follow the obtuse and labyrinthine instructions, and forget about it. For Mozilla, it's always an obscure flag in about:config.
Most of the time these are differences for the sake of being different (a marketing advantage, apparently) - there's no advantage or utility or even consensus on what is best. Why is three horizontal bars better than a gear, or a wrench? Why does customization even need to be at the top level?
I realize that as a developer you want to provide me with a rich user experience, but there's significant advantage in making it the user experience I'm familiar with in my OS and in my other apps.