I flew with Air Asia just a month ago. I felt it is very good, worth the journey to Macau Airport.
The fare is way cheaper than flying directly from HK, because HK-KL route is a monopoly route. My Air Asia ticket costed me around $700 rtn!! (incl everything)
The check in process is so fast. I think it only takes 30sec for the staff to check me in. Take note that Macau airport is super-small. There is only 8 gates and less than 10 shops there, so be prepared!
There is no FREE service onboard (no free newspaper, no free meals, no headphones, no pillow, but at least there is toilet paper) They do sell instant noodles, drinks and snacks. It is free seating. That means fight for the seats if you want to sit together as a group.
One thing negative is walking between the terminal and aeroplane. It is not much of a problem in Macau, but it is in KL. There are no help for disabled so you help yourself.
Before you book, of course factor in the ferry ticket cost, transport cost from Ferry Terminal to the Airport (Both way)+ Time consumed. Compare it with China Airlines before you book.