The Yoga 2 Pro is very usable as a tablet, in my experience. Not as good as a Surface, obviously, but it is very usable, and in return you get a much better laptop experience.
- 8 hours productive use on my desk with 3 monitors (form factor here is irrelevant, I just need a decent intel machine here)
- 2-3 hours mostly consuming use on bed and sofa (no need for keyboard here)
You could say that I just should use 2 devices but why should I when I can have it in one device? Another big point about the Surface Pro 3 vs other products is that you can use it for notes and drawings. There will always be compromises in 2in1 devices. For me the SP3 is the best 2in1 till now.