Speedbird -- as an AA Emerald I can tell you that after many legs on BA, QF and CX I have been very well treated. Particularly with regards to waitlisting for flights (even when waitlisted for a discounted QF ticket I had top priority and a confirmed seat came through within a day). Also, the oneWorld carriers all try to seat Emerald passengers in coach at the front of the cabin.

It is early days yet and I expect we will see further advantages come out as the alliance matures.