I went from a laptop + tablet to just a Helix. I like it. Web browsing is just so much nicer on a real PC in tablet mode than on either iPad or Android. I can access all of my docs in tablet mode. For reading, this makes sense for pretty much all of them, even using desktop apps. For some, editing in tablet mode makes sense, again using desktop apps. And I can pop it into the keyboard in a second if I need to do serious editing. It's more convenient to carry just the one item around, and I don't have to shuffle files around. And I have enough storage to get serious work done even when I don't have access to cloud storage. I never have to wish I'd copied a file to my tablet before leaving.
I wish the tablet mode were even lighter and thinner. I wish the battery lasted longer, although it's never run out on me. But it works as is, and I expect them to get better in the next year or two.
I don't use Modern UI except for a very few settings tasks. Until Modern UI Firefox comes out, I probably won't use it for anything substantive. I added a start menu that lets me boot to desktop. And Windows 8 desktop has some nice improvements over Windows 7. Win 8.1 promises even more, including different scaling factors for the device display and my desktop monitor. It ain't perfect. But neither are android and ios. For *me*, this works better.