Its a double edged sword.
Some of the things that make Xiaomi great, also are the reasons that make them bad. Its good to say that most of their features probably wouldn't pass CTS testing of Android. Thats why they had to remove GApps (my guess), and why they continue to re-make everything to use Baidu instead of Google.
Having Hugo join is great as they will probably start a long (12-18 month) process in order to become a more developer friendly company without abusing licenses like GPL. Though, what makes Xiaomi different and powerful and different is the huge amounts of code to AOSP to make MIUI.
You don't see Samsung, HTC or LG pushing their customized s**t back to AOSP. (Maybe bug fixes and the occasional tiny AOSP feature). Based on at least the decompiling of MIUI stuff, there hooks into AOSP are hacky and definitely not up to the standard for AOSP.