It's important to keep in mind that there's a difference between a mega smartphone and the so-called "phablet" concepts seen in the Galaxy Note II, which incorporates a stylus and extra media apps to give a more tablet experience. The Huawei Ascend Mate doesn't incorporate any of a phablet's bells and whistles, such as photo editing software or word processing tools. Also, the Ascend Mate is actually bigger than the Galaxy Note II in absolutely every dimension, effectively blowing the phablet's size out of the water while remaining every respect exactly the same as much smaller and sleeker phone models.
The phablet/big phone contrast really highlights the core problem of such a large smartphone: when you buy (and use) one, you aren't getting any extra features except a larger phone. There are no special OS adjustments or noticeable resolution differences when interacting with a bigger phone, so the only benefit lies in the major screen. It's even more of a challenge when considering the hardware limitations of such a large phone: a bigger screen means a bigger battery, and a bigger battery means more weight to add to that hefty size. It's not only two to three times larger than the average smartphone (which ranges between 3.5 and 4.5 inches), but has the potential to be that much heavier to boot.
Are we destined for a continuum of similar-looking and similar-functioning technologies that don't provide more beyond their relative size? Only time will tell, but it's prudent to warm up your hands the meantime for the bigger future.