It indeed is a great learning experience.
And a simple software renderer running on Symbian OS landed me my first real job
Though I think the use for them is really limited today, when most mobile phones (even low end ones) have a GPU.
And the ones that don't might be hard to run 3rd party code on.
Possibly in some embedded system, but then again, if you want advanced graphics, you might choose a system with a cheap GPU instead.
In some hypothetical system where your GPU is overloaded, but you have lots of CPU cycles to spare, I guess it could be useful for some multipass effect. (would probably need to be a unified memory system, preferably with texture streaming enabled to avoid copies, to be efficient though)
Edited by Olof Hedman, 28 November 2012 - 07:55 AM.