Here are two of the more annoying changes that I've found with Mountain Lion.
For the longest time, I resisted the marketing push to move to Mountain Lion (and Lion before that), happy and content with my rock-solid, stable, and speedy Snow Leopard-based iMac system. It did everything I needed, it would literally run for months without a crash or hiccup of any kind, and honestly, many of the changes in the newer operating system versions didn't strike me as compelling. (My laptops, which see less use, were upgraded, so that I could see things as many of my company's customers see them.)
Eventually, though, the pull of newer Mountain Lion-only apps, the need to test some stuff in "high DPI" mode, and a desire to run an App.net client (there are none for Snow Leopard) swayed me to upgrade the iMac. Overall, I'm quite happy with the results--many things are notably faster than before, and so far at least, it's been quite stable.
However, there are a few user experiences that are much worse than they were under Snow Leopard, and I'm not sure I'll ever adjust to them. Here are two of the more annoying changes that I've found with Mountain Lion.
Scroll bars are the evil empire?
So why does Apple seemingly hate scroll bars? In Mountain Lion, they're invisible, they move in the wrong direction, and there are no longer scroll arrows at each end of the bar.
Of these changes the invisible scroll is the worst: an invisible scroll bar is a useless scroll bar. Without a visible scroll bar, a user is required to take action to reveal the fact that a dialog or window contains additional information.
Without taking any action, it's obvious that the Get Info window in Snow Leopard has more to share with the user. In Mountain Lion's default setup, I have to scroll-drag in every single window to see if there's additional content. You can set them to be permanently visible in System Preferences, which I always do, but they're invisible by default. A user new to the platform, though, would have to discover this fact on their own – and it's not obvious where to go to change the setting.
The backwards scrolling also drives me crazy; Apple calls this "natural" scrolling, while I call it "insanely stupid scrolling." The change was made to match the way people scroll iOS devices. However, interaction on an iOS device is directly with the screen, and it makes logical sense that the content moves the direction your finger moves.
With a trackpad or mouse, though, you're more directly affecting the scrollbars, not the content, and it seems completely backwards. I tried it Apple's way for more than a day, but was much happier after I disabled natural scrolling.
Finally, and this may seem like a little thing, but Apple removed the scroll bar arrows from scroll bars. These arrows were very useful, especially with the option to have both directional arrows at one end of the bar: I could quickly scroll up or down with nothing more than a trackpad tap and a slight mouse movement.
Now I have to use a scroll motion with my fingers, or drag the scroll bar's thumb to accomplish the same result, and both of those actions require much more finger movement than did the scroll arrows. Over the course of a day, these little motions add up, so much so that I'm now using my arrow keys for forward/back scrolling more often than I am my trackpad.
Color out, bland in
First, it was the Apple logo itself, going from multi-color to clearly more-elegant-but-oh-so-boring solid black. Now it seems the same is happening to OS X. While the removal of color can be seen in many apps and system widgets, to me it's most obvious--and most impacting, and not in a good way--in the Finder.
In Snow Leopard, color in the Finder's sidebar played a key role in making it easy to visually identify click targets: The Applications folder was the red and yellow A-shaped icon; my home folder was a white house, the Desktop was the purple galaxy, etc.
Now, in Mountain Lion, while the basic icon shapes are unchanged, the color is completely gone. The Applications folder, home folder, and Desktop are all now just gray blobs. And even though they have distinct shapes, it was the combination of shape and color that made each easily distinguishable. As a result, I have a much harder time finding my click target in Mountain Lion, and find myself reading the text next to the icon to make sure that I have the right one.
Where do we go from here?
As noted in the introduction, I generally like Mountain Lion a lot. The issues with the sidebar and color, however, make using it more work than it should be. At least most of the scroll bar issues can be reversed (but really, they shouldn't have to be), but adding color back isn't so simple. I have hope, though, now that Jonathan Ive is in charge of all user interface design--perhaps we'll see positive changes in 10.9 and beyond. For the sake of my overly-scrolling fingers and color-deprived eyes, I hope that's the case.