Microsoft to make the case for Windows 10 on both PCs and phones

Say you found yourself in a Best Buy, or one of those retailers where everything on display was automatically described as "cool."  Someone hands you a phone and it has Windows 10 on it, and you say, "cool."  And you see a tablet, and it has Windows 10, and there's a laptop with Windows 10.

What do you think at this point?  Are you thinking, "Does this mean I can run my same software on all three of these things?"  Or is that not something you really need to do?  And if it's not, then what's the big deal about Windows 10 being "everywhere?"