Only one comment: if we cannot OC it to 550 Mhz or higher, we cannot earn back the costs for trying (added hardware costs should be earned back by the gained OC hashes).... But, we have a nice hobby anyway 
From what hno(KnCMiner) and Luke-Jr(bfgminer author) were discussing last week in IRC,
relating to driver for bfgminer on Neptune hardware,
the required details are in the published open source cgminer Neptune driver code.
Lots has changed (my interpretation of KnC statement)
Luke-Jr implimented many core details for Oct and Nov product and seemed to already understand the impact.
I got the impression he has much of the foundation already in place.
I rely on bfgminer to maximize output on 28nm boxes.
HW error down to the core level is essential for hunting down last few %.
I'll point out Luke-Jr did not indicate he would do it or when.
Evidently Luke-Jr had already inquired with KnC and got a non answer answer regarding whom to best discuss with.
That question got answered, no idea what Luke-Jr's future plans or timeline are.
A test/development platform may have been discussed
I recall compatability of a Nep cube with existing BBB in Luke-Jr's posession was discussed.
One can hope and politely show interest to both parties.
Luke-Jr had a throw BTC at him option for priority adjustment, he may still, if anyone is so inclined.
also this tidbit
"cgminer 4.4.1-knc3.4. Major CPU performance improvement ........"
From 7 days ago.
rc10 source is sitting ready to compile on git for the adventurer.
https://github.com/KnCMiner/meta-kncminer/tree/neptune/recipes-kncminer
Having an IRC client logging #kncminer (for personal use only) is often helpful.
A good second source for solutions to KnC related questions.
I happened to catch the above exchange live.
YMMV
