Any reputable sellers selling this phone? Or have it up for pre order? And what's the deal with the 3g in this phone? I hear it's wcdma only, and not lte?
As with the Xiaomi Mi 3, the first batch of Mi 4's will be for Chinese market and only support TDD LTE (4G). You will have to wait for FDD LTE version, for UK, Europe and North America.
When buying Chinese phones always check that the phone has FDD, and then check what bands or spectrum it supports. Some phones will have both FDD and TDD, but the FDD range may be limited to two or three bands such as 800/1800/2600, or 800/2600. In the UK we have spectrum's in 4G ranging from 800mhz to 2600mhz. These spectrum are also referred to as Bands.
Band 3 = 1800mhz Band 7 = 2600mhz Band 20 = 800mhz
Mobile phone providers will have different 'chunks' of the spectrum. Some providers will focus on one Band more than the other. The difficulty arises in knowing what 4G masts are in your local area. You want to avoid a situation where the phone you have bought does not have a band that corresponds to your provider, or if it does, your local mast only offers one band.
Offcom's mobile phone mast sitefinder
http://sitefinder.ofcom.org.uk/ is no longer acurate, as regulations no longer require providers to keep the data base up to date. You now have to rely upon coverage maps, which are not always accurate, and also do not follow the same methodology. For example some maps will refer to coverage outside of homes, not inside, or 2G AND NOT 3G or 4G. Having said this, HDSPA coverage and data speed in my local area is better than 4G.