Packaged air works for some people in some cases, sometimes.
Have booked cruise air a few times with no horror stories on the provided routing. The biggest negative to us is that if something goes wrong and the airline has to issue a refund they refund to who payed them i.e. the cruise line. Still waiting at six months for a refund to be issued.
Each case is different. If you demand direct flights, avoid cruise air. If you just want to save some money and don't care to be a bit inconveinced, cruise air probably will work.
Free air is just a promotion that may save on the total cost.