The sins of the past, repeated
Those who ignore history are doomed to repeat it, and the Elite x3 sure does repeat the sins of the Motorola Atrix: It's awkward and underpowered for the role it seeks to fill.
Microsoft's crippled Office and Windows, combined with the dearth of Window 10 Mobile apps, mean that even when connected to PC peripherals the Elite x3 can't function like a real PC.
The peripherals options are confusing and vary based on your dock; user and IT alike will find the pieces hard to manage. Hardware makers commit this peripherals mistake repeatedly -- even UX champion Apple made that mistake in the 1990s' PowerBook Duo. HP should rethink the peripherals mix with the next iteration of the Elite x3.
Also, the phone itself is awkwardly large and heavy. I can't imagine anyone wanting to lug it around.
Maybe the concept of a universal PC that adapts to be a smartphone, tablet, laptop, or desktop as needed is one that should be filed away in the failed-experiments room. Or maybe one day, someone will figure out how to make the universal computer. In the meantime, two devices -- real laptop and real smartphone -- are still better than one.
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