There is an AC in every cabin, the seats are just fine and you can store your luggage in the overhead compartment. You can take a suitcase but this has to stay on the walking path, which is not the most friendly for other passengers.
Every four seats have two power plugs so you can charge your phone, tablet, or laptop. There are good toilets in every cabin. The whole train is clean and kept clean throughout the whole train ride.
In Malang are two stations, make sure to get off at the last one. This is where you see Jodipan, the colorful rainbow village of Java.
Food on the Malioboro train
Once in a while, a trolly with two staff members passes who offer you an assortment of water, coffee, soft drinks, snacks, and Indonesian food. The Indonesian food costs us 25.000 IDR (1.70 USD) was fantastic and we even received snacks from a friend we made on the train.