m2uk: BA's FFP is an excellent high-end product, if you fly Club Europe or Y or B class in Economy. If you fly discount economy then don't bother.
If you want to use an AY card, it doesn't have to be a codeshare flight - AY are part of OneWorld.
For comparative purposes, I have Finnair Club VIP and I don't think the Finnair program is anywhere near as good as BA's.
I also have BD Gold and wouldn't dream of using the BD program. If I fly BD I will plough the miles into UA, LH or AC.
Nick