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