Have been frequenting AB for the last 7 years and the only reason is because this is the only place in the whole of Mumbai that serves true GSB (Gaud Saraswat Brahmin) veg fare and also tastes very close (sometimes even better) than what you get in restaurants of South Kanara/Udupi/North Kanara districts of Karnataka. To begin with their sambar is something you can have everyday and you will not get bored. Idli, vada, dosas, bisibelebath are all great and I will not waste further time on these items. Their specialties are something that must be tried and worth mentioning in detail. Here are some of my favourites:
1) Biscuit Rotti: A true GSB snack, which I have not found in any other restaurant in Mumbai. This is available only on Sundays (Gets over pretty fast so dont be late). This is a like a kachori and tastes very good. Goes well with sukka chatni and in between coffee sips.
2) Buns (Bun Puri): A couple of other restaurants do sell it but nowhere close to the ones at AB. You can have it plain or with sambar/coffee/dal (whenever available).
3) Dal Sevai: Rice noodles dipped in dal. Not regular on the menu but worth trying whenever it is available.
4) Rava Adai: Another classic which should not be missed whenever available. Goes well with mulgapudi.
5) Poha: Not the poha that people are used to in Mumbai but dry puffed rice mixed with grated coconut and special masala that they source. Goes well with dahi, upma or channa.
Other must try items are mysore pak and banana chips. Last but not the least dont miss their filter coffee which is definitely amongst the best.
The ambiance, feel and service are like any typical south Indian restaurant and all the items are very reasonable. A good meal for 2 should not cost more than 250 bucks.
Finally there is no hard sell-marketing like the other restaurants in Matunga (owner eats in this restaurant or our top ten items or awards received etc).