You know, I'm not a fan of this venture but I really don't want it to be any kind of flop, critical or financial: Neil has given me too much wonderful music over the years to be so petty and vindictive. But I can't help recalling how other non-Buckingham line-ups fared over the years. Remember Rick Vito and Billy Burnette? Exactly. That line up and their one album have largely been forgotten by FM fans and the public in general, and I suspect that this whole event will only linger in the mind of Neil's fanbase. Fair play to him for jumping at the chance, but at this point in time I can't really see either party coming away from it with their reputations enhanced. That's not to say they'll be sullied either though.
Having said all that, I'm really not surprised sales are slow. If a key member of ANY band was removed from it and a relatively unknown replacement was brought in, I suspect sales would fall.