It is an impressive piece of software, and there are lots of other low(er) cost alternatives to Photoshop; but I think the broad appeal of GIMP is that it it is

It is an impressive piece of software, and there are lots of other low(er) cost alternatives to Photoshop; but I think the broad appeal of GIMP is that it it is free in the GPL sense of freedom, not just as in beer and that can't be ignored in any discussion of the software. Also the fact that you can use it fully offline