I bought my device in the first flash sale and have been using it since then, I have not had any serious issues with it, I love the phone as it never lags and the MIUI provides a lot many features with regular updates which I receive even now unlike the other company devices which receive support for less than a year.
I like it’s built quality which is also very good though the device is quite, at first I was reluctant to buy a unibody device considering battery life but I have not faced any issues with it. The updates have been improving the overall user experience.