Tier points are definitely the most frustrating part of the program. If some tier points were awarded for discount economy fares, instead of zero ... I think it would be far less frustrating.

Also frustrating is no mileage credit for AA flights booked in L or Q classes.

As for customer service, I believe that BA discriminates in favor of their elite members ... at least as a gold member, I feel that I've received very good service from the BAEC, and prompt crediting of missing (or incorrect) partner flights.

A few positives about the program that I didn't see mentioned elsewhere:

BA has some attractive award redemption levels for flights to Africa compared to other airlines.

Good selection of airline partners for award redemption.

Elite members have access to AA Admiral's Clubs and Flagship Lounges when flying AA domestically (plus drink vouchers in the AC).

100% mileage bonus for gold members on BA and AA flights. (Only 25% bonus for silver members which is not as good as in other programs.)

Relatively recent triple miles promotions (last spring and fall) for transatlantic flights in full fare WT, WT+, CW or First were a great way to get extra miles. Hopefully we'll see another similar promotion soon!

Upgrade availability with miles to Club World is generally good as it seems to come out of "D" inventory instead of a special award inventory.

The on-line award redemption system has been improving significantly lately, and now lets you book awards that include stopovers in London. (No on-line redemption for partner airlines or codeshares.)