I've sumarized below a few of the issues that I've had since upgrading to Mountain Lion, I'll be sending this to Apple later today via their contact links. Whether it'll do any good is hard to say, but there are other avenues of approach to having Apple behave in a polite and helpful manner toward it's users. Hopefully I won't have to go that path.
OS X Mountain Lion, Usability Issues
Several changes in Mountain Lion (and previously, Lion) have created usability issues.
1. Scroll bars have lost their arrows and the bar, or 'thumb' itself is thinner. Working on long text files sometimes requires fine vertical adjustment of the text, this is not possible with the scroll bar 'thumb'.
2. The hand tool is missing in Preview. With large sized files, moving around in the image is really inconvenient and requires several scroll bar moves.
3. Folder icons are now all grey with no option to modify. This hinders usability because you have to visually hunt for the right icon whereas previously unique, customized or coloured icons were quick and easy to identify.
4. Software Update now works through the App Store app.
This is a problem because currently there is no way of seeing the file size of each update download and worse, there is no way of pausing and restarting the download. Some downloads are very large, ie the OS X update was over 4 GB, losing the download whilst downloading means re-downloading and loss of monthly data plan capacity.
Other:
5. There is no way of reporting abuse on the Apple Support Forums. The result is that trolling is easy for perpetrators and annoying for forum users. Moderators need to be aware of this. We need a 'report abuse' link.
There are a lot of things I like about OS X Mountain Lion, but I think the above issues need addressing fairly urgently.
In summary, most of these faults have been obvious for some time and yet there is no response from Apple. Certain users, like handicapped people and professionals have written about their problems with these usability issues. As a writer I find text navigation in Pages really awkward, as without scroll arrows the text moves in jerks and jumps which becomes very tiring and tiresome over a long period editing. (I moved to Pages btw because MS Word had become extremely problematic, misbehaving bloatware)
Additionally, I do not have a trackpad or a scroll-wheel mouse and don't see why I should have to buy these devices (I have a limited income) simply because Apple has reduced OS X usability in order to promote a new tablet-like interface, legacy users would certainly have a very dim view of this.