Had my first Batu apple, a fruit the folks around Malang are very proud of in East Java. It grows above 1000m elevation around 8 degrees south latitude. See photos at drmala.blogspot.com
Having had a farm in Nova Scotia, Canada with some old apple varieties and lots of fruits from seeds in surrounding abandoned orchards, I can rank the Batu apple I had as follows:
10 - any really good backyard variety or really good pippin eaten fresh in Nova Scotia
9 - well developed Fuji in a supermarket
8- Cortland, McIntosh in supermarket
6 - Granny Smith in supermarket
4 - a bad seedling apple in Nova Scotia, which occurs about 70% of the time
3 - a really bad seedling apple in Nova Scotia which occurs about 1% of the time, like the pippin my friends named, "Tart Vomit"
2 - a Batu apple (which has a thick skin, little sweetness, little aroma, little acidity, overly hard flesh, and an unpleasant bitter flavour.)