The overall design and feel of the Mi 4 were well received despite an uninspired design that reminded critics of the iPhone. Ars Technica says the phone's "impeccable construction makes this the best Android hardware we've seen all year," while CNET says they "like the feel of the phone" as it sits "comfortably" in their hands. The frame houses a 5-inch 1920 x 1080 pixel display that Android Authority finds "vibrant" and Mobile Geeks calls outright "fantastic." However, PocketNow had issues with the display's "warm" picture and "side visibility," which they say can "taper-off" at certain angles.
The camera of the Mi 4 is a mixed bag, where as Android Authority calls it "unremarkable" and Ars Technica finds the photos "a little on the warm side," CNET was "impressed" by its performance and Mobile Geeks even managed to get some shots that were "simply stunning."
Xiaomi's real standout feature is the MIUI Android skin, offering a bevy of customization features. Ars Technica says it's "ridiculously fast" in spite of all the changes, even finding it "faster than stock Android." Unfortunately as this is a phone aimed at the Chinese market, there are a lot of places that went untranslated. PocketNow also found a "darker side" to MIUI, noting quite a few "quirks, bugs, and glitches." However, Xiaomi recently put out an update that hopefully squishes a few of those bugs.
Should you buy the Mi 4? It depends. If you're looking for a well-designed phone with a totally different Android experience, and it will work with your carrier, then sure. Keep in mind that Google Play is not loaded on here, so it'll need to be side-loaded. If that's not the kind of user experience you're looking for, there are plenty of other options offering more familiar and accessible experiences.