Asus has been trying to nail down the modular mobile device for some time now, but the PadFone X is the first iteration of the company's tablet-smartphone hybrid to reach the U.S. Was it worth the wait? In the age of digital omnivorism, yes, but with some qualifications. Asus hasn't arrived at the perfect union here; as a smartphone, the Padfone X is capable, but unexciting, and as a tablet, it's clunky and has some performance issues. That said, the device is an unbelievably great deal on AT&T—$199 (with a two-year contract) gets you both the 5-inch PadFone X and the 9-inch PadFone Station. The shared data connection and combinable batteries help mitigate functional shortcomings of either device alone, making the whole greater than the sum of its parts. Still, if all you need is a new phone, there are better standalone options, like the Samsung Galaxy S5 or HTC One (M8).

Design, Dock, and Call Quality

Form follows function for the nondescript, rather utilitarian PadFone X. The rounded, soft-touch plastic back fits comfortably in the hand and an angular, faux-metal band facilitates docking, but it lacks distinction or character. At 5.67 by 2.85 by 0.39 inches (HWD) and 5.29 ounces, it's the same width as the Galaxy S5 and a touch thicker than the HTC One (M8). Volume and Power buttons are on the right side, but the latter is situated too high, making it hard to reach conveniently with your thumb. There's no visible notch along the edges, but with some uncomfortable prying at the micro USB port, the back cover does peel off for access to the SIM and microSD card slots, as well as the non-removable 2,300mAh battery. In my tests, the PadFone X was able to last for 10 hours, 15 minutes of continuous talk time.