Description of Problem:

The tip of the day that says,
(grr, I can't copy/paste it!)
When you save an image to work on it again later,
try using XCF...
claims it preserves every aspect of the work in
progress.  This is not true - undo history isn't
there, a very important part of the work in
progress!  Either say, "preserves the layers and
most aspects of your work" or, "preserves the
layers and every aspect except undo history".

(I don't know if the current active brush and
colour pallette are restored either, nor plugin
settings, nor other aspects that one might
reasonably consider part of one's GIMP work
environment)