Did you actually try to utilize Word, Excel, etc.? I type a lot, so tried it for 15 or so minutes in OneNote/Excel. Completely unproductive since I had to keep the keyboard "dug in" into my stomach. The experience has definitely improved over SP2, but still far from this being a fulltime device for me. Just for reference, I spent around six months with SP2, so know what the typing experience on SP devices is like, in general.
You know what I can possibly perceive that may solve the "extended runway" need of the taller Surface Pro 3 devices? A Type Cover that folds back the trackpad area.
I haven't tested the device in full of what I would usually do in sitting in a soft chair, hard chair, or indian style sitting. But from the extended "tallness" of the device, it may come close to not fitting compared to the 10.6 inch Surface Pro 2 (even though as I mentioned, I would appreciate the taller, bigger working screen for single window/screen display workings).
This would allow the entirety of the device deployment with kickstand use to fit on most user's laps and legs, typing, allowing the touchscreen for virtual trackpad, pen pointing, or direct touch manipulation.
If one is practically used to typing and thumb trackpadding on a typical laptop trackpad anyways with no direct conjunction of pen use - then again laptops are still available in all shapes, sizes, performances, and comfort (Yogas, Thinkpad Yogas, and the like are there for tablet handling conversions too). But the need to slide the cursor, is sometimes a slight waste of time for me. Trackpads for the longest time have not solved much in middle click issues either compared to a solid periphery mouse/trackball to the side - which I would have anyways (Surface Pro or laptop setup otherwise).
It is another reason why I am more inclined to stay on my Surface Pro 2, and preferring the 10.6 inch screen and 16x9 ratio. It is more sized right for me and along the Surface Pro lines allowing me to fully utilize all the periphery inputs (including the biggest one I do like - the pen).
With any Surface Pro lines having the cover system combined with the light weight, hardware in the screen area (slate/tablet design) it makes it more travel friendly if not always traveling with me.
Excel work and OneNote work for me is been very very useful. Cell work and selection done by pen, switching back to notes with the pen. Typing in both back in forth as well (though I seldom need to type in OneNote).
With the Pro 3, I can easily see Microsoft releasing a pen with both ends pressure sensitive, both ends being able to recognize tilt and pen barrel rotation (twirling the pen on the canvas and it would enable things like calligraphy). If they want to keep the pen power on options, a button on the side, near the top of the eraser end is in order, and still keep the two side buttons near the index finger area for other functions (menu pull down/middle click/right click). It is another "wrench" in my options.