I believe that when you have to do with a worldwide audience, you cant judge them all claiming that "they dont know" or "they misjudge Linux distros" or "it is because they are used to M$ products"
Look at android or iOS. they are not windows-like or windows-way and they are more succesful than Windows itself. Why? Because you live in 2013. You expect some basic things from an OS. You expect visualy-modern interface first of all. You expect simplicity. Simple IS better. You expect arrangement. You expect productive environment and fast (in terms of how quickly you find what you are looking for.
You give those basic things, you gain market share and then you have more support from computer gaints. Like it or not thats the way world works.
So Ubuntu is not gateway for me. It is a train station to a alternative "city" with its pros and cons against Windows 7 (the most succesful Windows ver.)
Gateway is Zorin OS for me and Xubuntu maybe.
I could include Linux Mint as a gateway too but they seem to me as completely Ubuntu depended. For example they released Linux Mint 15 in June for what, 7 months? Without encouraging the upgrade after every release?