After four years of teaching students embedded C#, I can confidently tell that Visual Studio is the biggest hurdle [em]by far[/em]. Every year. Too many windows, too many buttons, too may options, too many files and know-hows, all thrown into the face of a first timer at once. They accidentally close one window (Debug output, Toolbox, program.cs, you name it), and they stuck immediately. Because they don't know how to reopen, and, most of all, [em]why [/em]would they want to reopen it.
And then comes all the platform perks. Target framework version — what? Platform x86, ARM — WTF? Deploying to emulator, COM, USB — even I do not want to care about it, why would they?
Visual Studio is the best, true, but only for professionals. Newcomers rarely are professionals. All they care is to flash a LED, measure temperature, maybe do some other tiny little thing. Installing multi-GB hog that Visual Studio is quickly turn excitement down, and an opportunity to hook them up is lost.