The Detroit Borg does a nice and thorough 4K unboxing/review of the Asus PadFone on AT&T.
TL;DW Excellent phone, tablet a little clunky.
My take: The hardware to make this able to dock a phone seems like more effort/space/cost/etc than just making a separate tablet. If OSes had better “continuity” and carriers would just sell buckets of data across all devices, there would be no need for something like this. Until that time, this will definitely hit a niche market.