I think that the main attraction is the promise of laptop grade productivity. But it has to do everything as well as both a windows laptop and an iPad. If it does only one as well (or better) and not the other, people will just buy the stand alone device that does it better I bet.
It does however look great. The I like the way they made it more usable as a semi-computer with the keyboard and the stand. This way you can actually get some work done with the thing insteead of just playing around (lets be honest, most tablets nowadays are big smartphones without the phone part, without any practical use cases).
I couldn't put my finger on any one particular thing tablets excel at compared to any other device, but overall I find them to be a very enjoyable, useful thing to have around. :D
I suppose most of my computer use consists of writing, so it's pretty often when I am using an iPad that I am reminded of what I can't do. Also, I'll sometimes switch from the iPad to my phone, because I want to make a note of something, or take a map route with me. I think I'd do some Hubskiing with Surface. The UI will probably be much worse than the iPad, however. :/
Long story short, I didn't say that a tablet is useless, just that it is not as usefull as it could be (which might be fixed in part by the MS surface). As for the reason I don't want one, I'm paranoid :P
There's also the Vivaldi Tablet, which also runs plain Linux and uses entirely open-source software out-of-the-box.