I a using and appreciating more and more Devon Think in my work.
I find it very powerful, flexible, and finally convenient for serious, massive work.
There is just two items I would really like to see improved: the rendering of text typos and models:
Texts always appear tiny by default on my screen. Also, when I print a rtf text, there is always a large blank column to the right of my page.
I hardly use any text models at all, as I find them ugly. They could make some use of fonts, color and perhaps icons. Table sheets are also a bit difficult to manipulate.
Hope those suggestions help.