Actually, I just hand them my phone and say "Play around with it."
Most of the time people just say "Eh...", but then I go on to say "Did you notice this..." and show them various things. Like resizing and rearranging the tiles, then point out that the tiles are "live" (android people like this, instead of widgets) and you can also nest tiles into one tile. Then they say "Oh WOW, that IS cool!". But then they ask, "So you still have ALL your apps on the main screen

" To which I explain that I only have the apps that I use the most on the main screen, and that all the apps are listed when you swipe left (iOS people always say "I wish Apple would do this.").
The hard part is when they ask about app availability, and I have to explain the situation. There are official apps, then third party apps. If there isn't an official app, there is most likely a third party app that will work. Abet some do it better than the official app, others not so. But with the new paradyne of universal apps that go from PC to Mobile, and that Microsoft has really put an effort into Visual Studio so programmers can write once and port relatively easily to whichever platform (Windows, Windows Mobile, Android, iOS) they like, there
should be a growing increase in app availability. But I have to admit, time will tell.
One other thing, after I show them the tile features (rearranging, and such), some people ask if this will work on their PC with Windows 10. I have to explain to them, YES! You can, and should, customize the start screen to what
you like. I'm always stunned at how many people leave their start screen "as is" on their PC.
I seriously blame Microsoft and their US marketing department for this. They try to mimic Apple ads to much. They should start over with an ad campaign showing off the features and the details of Windows 10 (PC and Mobile), similar to what I've seen in other countries. Which explains why Windows Mobile is doing so well,
outside the US. More tutorial type of ads, if that makes sense.