A major disadvantage of the booking codes, is that outside of domestic flights, one can not get the 25% COS bonus, on discounted business class fares.

For most other Star Alliance carriers (are there any exceptions), one can get the 25% COS bonus. That might induce some (including myself) to go on the other carriers, perhaps for that reason only, if the ability for one to reach a certain Aeroplan tier level is touch and go.

For US flights: UA (and soon to be Star Alliance member US Air?), their front cabin in their 2 cabin planes is classified as "first class" and earns 50% COS bonus - will the new AC transborder fare structure (to be introduced by April?) reflect this policy and allow for a 25% COS service on C fares, and perhaps a 50% COS service on J fares (as is the case now, with domestic AC flights)?