I have personally never used Air Asia in the past. However, it is one of the better budget airline according to Skytrax. I believe Air Asia was voted best budget airline in Asia and made into top 3 world wide. Delay could occur to any airline, Air Asia record 85% on time performance in their last report.
You can check in your Virgin Blue flight at home, do that before leave your home, it should help.
Yeah, I think its 24hours prior your departure. You can print out your boarding pass at home, when you get to the airport, just drop off your bags in Virgin Blue's counter.