This is all about change. The way data and information are going to be handled in the future is going to be different.
The start button in old windows simply provides a list of apps or programs some of which are fixed and others which can be added or deleted. Most people probably don't do the latter. The 'start' screen in 8.1 appears to me to be just a graphical version of that - and yes it is designed for touch but that is where the next change is coming. In fact the start screen in Win8 is the same it just doesn't have the word 'start' on it.
If data is being stored 'in the cloud' we don't need big PC's with hard drives and so forth. We shall have smaller user interfaces on which our data is displayed. The Surface is a forerunner of these. The Lenovo Yoga things are similar just going at it in a different way. when you need touch you use it as a tablet, when you need a keyboard there it is.
If I need a bigger screen then I will mirror things on/or use the TV.
I use computer devices for a number of things - music, images, work and social. I don't play games - they're not my thing.
I can really see me ending up with a surface or some other convertible tablet - screen about A4 size - and a windows phone. If I am a typical user then I think MS have it right. (No connection)
Change is often hard to take - but it inevitably happens.