This is good stuff! I have been chewing the other end of this lollipop recently, by rolling my own inductors and transformers.
I'm only doing a few, but it is apparent that for big runs the economics of the inductance are really important.
I found that 80% Nickel lams are around 2.5 times the price of 50%Ni/Fe, for the same quantity of lams (buying by the kilogram). And they give you around 2.5 times the inductance for the same size and number of turns.
So switching to the higher cost lams can either save space, or let you use fewer turns and bring the DCR down, which can be desirable in some applications.
The measured inductance does change remarkably with frequency, which does screw with the theory. Eventually of course you have to measure how it performs in the circuit.The document that Marik posted here is really helpful and worth linking again...http://www.groupdiy.com/index.php?topic=47497.msg597825#msg597825
Of course the more subtle effects of saturation, hysteresis and the elusive 'tone' are harder to measure and understand.
Anyway, thanks again for sharing these results.