I purchased this phone for use in the UK and have been delighted so far. I made sure the seller sent me one with the original Chinese ROM, not a cobbled together international ROM.
The phone has downloaded over the air updates in England and did not even need to use a China based VPN, it all worked just fine. I have installed Google Services and Google Play, again all working fine.
The only downside is that the phones only built in languages are US English and some sort of Chinese/Mandarin, which means that Google maps navigation speaks with an American accent rather than a British one. I can install British text to speech, keyboard and dictionaries, so it really isn't a problem for me as Google maps is the only application I have found to be affected by this.
The Chinese standard ROM does not have an app drawer, which is astonishing, but easily fixed by downloading an app drawer from Google Play. All your unused icons can be neatly tidied away in a folder on one of the home screens.
The storage appears lightning fast to me, so I would not worry about the benchmarks in this article. Most phones of this price come with a small internal memory and you have to use an SD card for storage, which would be much slower than the built in memory.
There are loads of types of case available and they are so cheap to order from China that I ordered 3 different types at the same time as I ordered my phone so that they arrived at the same time.
In summary, this phone is a huge leap up in capability from my Galaxy Note II, which really used to struggle with google maps. No problem at all for the ZUK Z2. The 5 inch size is smaller than my Note II and in my opinion it is the perfect sweet spot for ease of use.