It's difficult to rate the alliance when the interface is with one member airline.
I have the misfortune to have rather a high number of Flying Blue miles which I am keen to redeem. Apart from the above comments, I would add about FB:
- general inability to book DL and other partners' award flights online;
- award availability online at delta.com? Yes. Same flights available online at FB? No.
- no 800 phone line in UK, just a high cost 0870 number or an international call to France.
As DL let me book online and also have a local UK number, it is clear to me that the alliance is being brought down by the lowest common denominator, in my case AFKL.