Whats the rom version that you installed?
I'm using stock firmware that was preloaded on the device. No bloatware. There was and update after I switched on the phone.
I had two updates recently (one today actually) and I'm happy to see the updates are small (7.2MB for bug fixes and optimizations) and that it does get updated often and not have to wait like for other manufactors that usually also first push it to the mobile operators etc..
MIUI 7.2.3.0 LHMMIDA Stable, Build LRX22G
I'm very happy with the stock firmware/rom on here and everything works perfectly. It's the international (EU) too and not the Chinise one.
This phone reminds me alot of how Google Nexus devices are and good clean firmware/rom. Not sure if you do buy any other Xiaomi device at any operator if they flash it with their custom rom with crap, etc.. but the stock rom is availble on their site to download for the device.
Battery life is not bad and plus the battery is removable and replacable later, so far it's at 20% this morning after being on for 14+ hours, but with light usage and mobile data on (not wifi).
Speaking of data, I'm very happy to see that even with all my apps installed (whatsapp, facebook, twitter, 9gag and so on) that usually always 'ate' all my data in the background, it uses minimual data. Even the system apps used more data on my previous android devices. Just goes to show how bloatware 'eats' your data.
You can goto security settings and choose what apps to use what connection (mobile data or wifi). Also had a built in virus scanner with two definition sources and that spares the load for installing other virus scanners (you have to manually scan, but that's fine with me).
You can find this under 'settings' 'system apps' 'security'.