Thanks for all the input folks.
I had a good think, and although it feels somewhat like a waste not to share some of my most useful experiences, I don’t think now is the time for the book I have in mind.
There are several factors depressing the Excel development market at the moment, some are permanent trends, some I think will reverse in a year or two. In particular there is a heavy regulatory downer on Excel just now, once people get caught messing up in the replacement technologies that focus will move off, allowing people to get back to the benefits of Excel.
Also IT departments currently have a big veto power, I think once people notice that that doesn’t actually move the business forward their influence will decline, allowing people to get back to the benefits of Excel.
On the other hand the time may really be up for professional Excel development.
Either way I’ll still chip in here with points of interest.