I agree entirely, it is a valuable tool for filling in the blanks, and I enjoyed the process (and the learning) immensely when I did that sort of thing (I could be persuaded to do it again, in fact).

There is an obvious problem, though, when it goes beyond "filling in the blanks" to "overwriting" other evidence.

And, I hate to say it, but there are other problems as well. Experimental archeology may, for instance, come up with one or two good ways to sharpen a quill pen (to use your example), but experimental archeology cannot ever demonstrate or prove that that's the way it WAS done.

It's entirely possible.. even likely.. that our ancestors knew some tricks, now lost to us, that took generations of THEIR ancestors to learn... and it's even remotely possible that a modern counterpart might stumble on to a different, or even better way to do something than was known at the time. There was probably nothing preventing colonials from making, say, fire pistons, other than the fact that nobody had thought of it.

But the bottom line is that the best possible result of experimental arecheology is to demonstrate how something could have been done, how we think it's likely it was done, but it can never have really conclusive results. Other forms of research can.