Whenever I get on a new Windows machine, the first thing I do is switch off the annoying defaults which hide file extensions and conceal hidden files in Explorer. Fortunately, that task is a lot easier on Windows 8.
I can half buy into the logic of keeping system files hidden, if only to stop less experienced users erasing them. But being able to see file extensions is handy even if you're normally happy with letting the default application launch them. (Incidentally, the Mac has the same default behaviour, and again you need to drill down to switch it off.)
In earlier Windows releases, you've had to switch these options by navigating through Tools —> Folder Options —> View and then deselecting 'Hide extensions for known file types' and 'Show hidden files, folders, and drives':
You can navigate to the same fiddly location in Windows 8 by clicking on Options on the View tab. However, the View tab also surfaces that feature much more directly, with simple tick boxes for File name extensions and showing hidden items.
The keyboard shortcuts are Alt-V-HF and Alt-V-HH respectively. Definitely an improvement. (If you're planning to test out Windows 8, be aware of the potential traps.)