Apparently after the transaction, I also got a so-called "Shake Reward". Better than nothing to promote use of the app.
All in all, an interesting experience. But other than promotions (which are not many), I don't see the value of using the app over credit/debit cards (that can get you points/cashbacks) and have a faster transaction speed (partly from the familiarity of vendors using card-based systems). And with the inability (I guess for now) to link to your cards, you have to top-up your wallet (preferably while not at the front of the line). My take? If the shop offers card-based transactions, I'll use that over Boost unless there are promotions/bonuses that give added value. If it's either cash/Boost, then maybe I'll use the app, but only if I won't embarrass myself topping up the account just enough to pay for the transaction/have an excess of bonus value to make the potentially longer time at the cashier worthwhile (it could get shorter as every one gets more comfortable).
Anyways, if you're interested in trying out the app, go ahead and use the Invite Code muhq2c0 to get RM 5 after your first mobile credit top up. Do try it out, if mobile cashless payment systems are your thing.