Microsoft has encouraged users to give feedback for their Windows 10 technical preview, and one way they facilitate that idea is with a UserVoice forum, where you can leave feedback yourself, as well as vote and comment on others'. Here are the top 15 current suggestions:
- Add Persian calendar to Windows
- Windows store for Iranian people
- Add tabs to Windows Explorer/File Explorer
- Make Windows free for everyone
- Please give the people of Iran to access the Microsoft Store. Thank you.
- Make Windows Update the one stop for all drivers
- Please merge PC settings and Control Panel!
- Redesign & replace ALL aero-themed objects in Windows 10
- Add support for .rar .7z and .bz2 file types within File Explorer
- Windows Calendar Event Support
- Provide a better Notepad application
- Bring back Aero Glass from Windows 8 Developer Preview
- Built-in support for multiple codecs
- Let me pin ANYTHING I want to the start screen (shortcuts and files and any other thing that I want, not just executables).
- Give us the ability to customize the Login Screen
As you can see, a lot of international users want a more optimized experience that is on par with the US version. Some of the feedback, however, is overly optimistic, and somewhat misguided. For example, making Windows free will depend on financial analysis, it is not really something you can request. Notepad priority is probably pretty low, as there is a lot of competition from coding (sublime text, Notepad++, Visual Studios, etc.) and editing (Microsoft's own Word, OneNote, etc.) perspectives -- however, a desktop app store could give easy access to those alternatives and reduce complaints.
The codec and file support feedback is the same since Windows 7. Not all these formats are free, and Microsoft isn't very open as to why they don't ship them out of the box. I am assuming it's not much different to why they no longer support DVD playback -- licensing. You can download alternative players that either license all the different technologies, or rely on open source projects, such as VLC, in countries where the law is different than the US (VLC's justification: "Neither French law nor European conventions recognize software as patentable … Therefore, software patents licenses do not apply on VideoLAN software").
You can view all the feedback, and submit your own here. This is only one of the ways to provide feedback, and since anyone can vote or submit, probably not as specific to Windows 10 as the feedback received through the operating system's built-in mechanism.