I had just upgraded my Huawei 4X from Lollipop to Marshmallow. Well, upgrade is really good. The main feature added in Marshmallow is screen recording. Overall minor improvements are there, but with regard to sound, I found the sound of the phone is heavily reduced after the upgrade. Not sure, but there have been some problems while calls being connected to other end and frequent disconnections ( it might have been the case of faulty network, so I am totally not sure about it) . But coming to overall performance of this phone, I bought it in 2014 and still going strong. Considering it was launched in 2014 and still able to support 4G network, I don’t feel my phone is obsolete in any means. ( bought Honor 5x in 2016 for a family member because of my personal experience) .