My own opinion tends to reflect what others have said already, but, if I may be permitted to put it in my own words:

I have had relatively decent in-flight experiences with AC; acceptable to good in Y, good to excellent in J. Interactions with AC ground staff at the airport(even excepting the incident linked to in my signature) have been less satisfactory.

The three major problems as I see them:

1) Mis-alignment of incentives between the staff and management. We may make snide remarks about WJ, but the employees there seem to have a much clearer interest in the promoting the company and ensuring its fiscal health.

2) Mis-alignment of incentives between AC and AE. As the two companies are now legally separate, their interests are starting to diverge, to the detriment of the overall customer experience.

3) Uncertainty about market positioning. Who does AC see its peers as? The in-flight experience may be somewhat better than the US legacy carriers (although, IMO, not enough to justify the price premium and loyalty progam differences (Tango in particular)). It does not, however, compare to the Asian or Gulf carriers such as SQ, NH, OZ, EK, EY, etc. (even in Y), so its boasts about "Best International Airline in North America" ring a bit hollow to those of us who have flown these airlines.

As to how AC can improve: the old cliché "Under-promise and over-deliver" is probably a good place to start.

TB-ES