For me, these are what I find useful.
1) I live currently in a pretty rugged area, so being built to mil-spec is nice, this phone is solid and added onto it the carbon-fiber cover its even stronger.
2) Long Lasting Battery - I liked my 950XL but the HP Elite x3 so far more battery life and seems to charge faster too. On a long trip in unknown territory this is truly a bonus.
3) Speakers seem to be better than my 950xl was, and those were not bad at all. That is for a mobile device, I still have yet to see any mobile device with speakers that really sound good, but these are better than anything else I have owned.
4) Continuum and the desk dock are nice, I love the way their desk dock very well put together. I also just ordered a Lap Dock and soon I will be able to comment on that, but I have read that others who have them love them.