Surfer,
I have tied over 20,000 spey flies during the last 11 years and have found the following about proper spey feathers.
Heron is wonderful, if you can find it. Keep in mind that it is illegal to collect your own in the U.S. And if you happen to find some legal heron for sale, you will pay a very high price for it (around $2.00 to $3.00 a feather). this makes for some very expensive flies.
Blue eared pheasant is a very nice substitute, which I use a lot whjen heron is called for. Mark has it as do several other suppliers, such as Angler's Workshop and most of the fly shops in Washington state. One of my favorite spey feathers is schlappen. It comes in nearly any color you want (although the grey is not dark enough for a heron substitute), it is cheap (unlike blue eared pheasant which runs between $150.00 and $225.00 per skin most of the time), ties a beautiful spey fly (shck out the work by Gobin and Veverka to see how well it looks on a finished fly, and it is very close to the original spey feather of old.
Also, you can use coche feathers (rooster tail feathers) which are the original spey feather from the 1800's. these are also fairly easy to find and are not very expensive either.
Dyed chinese pheasant rumph makes an eacceptable substitute, but you can not tie larger than a size 5 Alec Jackson Spey Hook with most of the rumph feathers available. Yes, there are a few found at the end of the rumph that will tie a size 3 Alec Jackson Sepy Hook, but there are not many. Anything larger than an Alec Jackson Size 3 and your out of luck with chinese pheasant.
I would avoid any of the burnt goose spey feathers because of their brittelness,as has been mentioned by someone else. They can be used, but you have to soak them in hair conditioner or glicerin for a couple of hours to make the stem pliable. Althoughthe stem becomes pliable after this, there is still the problem of therather large stem.
The Whiting Spey Feathers are indeed very nice to tie with. however, keep in mind that they behave much differently than heron, blue eared pheasant, schlappen, coche feathers in water. They are much stiffer and considerable thinner. Also, they are difficult to find at this time because they have just become available to the market. This will improve over the next couple of years.