> With 2.6.2 on Windows, I get filenames surrounded by {}, all in a
> single unicode string.

This string surrounded by { } indicates it is supposed to be a tcl
list, which didn't get converted but should be done by tkFileDialog.

> The change may be related to the new Tk library used, not directly the
> tkFileDialog module.
>

It could be, or not. A simple solution would be to call the splitlist
function from _tkinter on that string, which tkFileDialog should be
doing indifferently of expecting objects from _tkinter or not.

> (BTW, I don't see *any* unit tests for tkinter :( )
>

There are some one a separated branch for now, but it doesn't include
tkFileDialog yet.