I make some complicated animations, often with 100 frames or more (which could
take about 30 to 60 minutes to open up each file and save them individually). 
GIMP, as far as I can tell, doesn't have any feature that'll allow you to batch
convert files.  That is, save a bunch of XCF files as BMP files then save those
BMP files as GIF files.  I use layering to make moving the background objects
easier and faster.  Saving XCF files directly as GIF makes the layers as
individual frames and will mess up the animation.  A batch convert tool could
make making animations be faster to make.

And not just BMP to GIF, but like JPG to BMP, BMP to TIF, and many other common
image formats already available in the GIMP.  Basically, running a save as
command on selected files with the same name is all that's needed (like
example.bmp to example.jpg or testing.tif to testing.png)