There are many other places!. The Mega Mall is at the Batam Center (ferry terminal), huge building where you can find Matahari Dept Store, Hypermart (same as Giant), other smaller shops with good discounts, food outlets serve local, western, pizza doughnuts etc.. Just visited here on 30th Aug. Got some apparels at 50% disc.
At Nagoya hill you can also find Matahari, supermarket, food outlets and apparrel shops.
There are Ramayana Dept Store and other malls and shops at Jodoh. Cheaper here! If you don't mind the 'pasar malam' style and like to bargain, visit this area in the evening. The locals call this place as Pasar Jodoh.