It may take some getting used to, and at first speech recognition may not be as accurate as you'd like, but over time it will improve. The pace of dictation will also be a hurdle if you were a particularly fast typist.
As for the apps you can use with Dictation, you'll have no problem with Microsoft apps like Word or Notepad. But some third-party apps may not work at all. In my tests, for example, text editors like Sublime Text 2 and GitHub's Atom didn't work, but Notepad++ did.
More than just dictation
Once you've got dictation down, you can use the built-in speech recognition feature in Windows for all kinds of tasks such as to open and close apps, navigate menus, control windows, scroll, and even right-click. Again, Microsoft's help pages can help you expand your voice command chops.
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