I FLY MAA-SIN-MAA on AI regularily in Business as it is the only day flight from MAA-SIN till Silkair starts on June 14th.
Honestly, I used to get extremely irritated with the lack of service until one day I changed my perception.
If you look at it - it is a Premium Economy experience. You are paying near SQ Y or SQ Y+10% fares and in return you get:
1) Biz Check-in with higher Baggage allowance
2) Lounge Access at Both ends
3) A larger seat with more legroom
4) A more personalized meal service, but economy style tray with economy style beverages
5) Off late they've operating 321's so you get some inflight entertainment

Honestly, if SQ were to bring its day flight back with AVOD etc etc I would choose SQ Y over AI Biz.
I doubt I'll be switching over to MI at 2.5 times the cost in Business class and will not fly MI economy for 4 hours.

However, a little perception shift in expectation will result in a much more pleasurable AI flying experience. The crew try very hard and the pricing on this sector is outstanding.