Bro I am.on wired and the speed test show very good and suitable to play hd quality of movies.
I also tried to pause awhile to allow the buffering and I go do some other my stuffs but sometime I saw it became 0 kbps.
also I took almost a week to complete a 2hr movie captain America 2 which made me also almost threw the box from 20 storey all the way down.
There are many factors that might be the cause of your problem.. I assume you are using the build in test in the Xiaomi "native" test option in the network menu.. As the result is good so we can conclude that your physical network is not the problem. You should be able to play contents from Xiaomi iCNTV..
Many user use the Jailbreak version of Xiaomi with other UI (rabbit or other) which stream contents from various sources.. Some of these sources might not have a good network link via your Internet provider.. It is hard assume an ISP can provide link to all sources with good speed as IP traffic to China are the most expensive in the world today (how about said 20x). Most of the contents are still hosted within china but thing are start changing..
So the problem might be with your ISP provider network does not have the good link to the contents streaming sources. You should try out different "app" or select the "good source" to stream from.. Personally, I like to stick with native Xiaomi app to stream contents from it iCNTV which deliver via CDN 19, 26, 30 as my ISP seems to have good path to the sources..