I had an old Lenovo K3 note and had it updated to the latest Android 6.0 - Marshmallow. The UI is smooth now and touch response is much better now. Apart from this the major drawback seems to be the battery drain for most of the Android phones that received the Marshmallow update. The same battery drain happened for Lenovo K3 note. After testing it for couple of days I can surely say that the earlier Lollipop version was good as far as the battery was concerned. Anyone facing problems of battery drain after updating to Android 6.0