Your right, Cocos2D was a big influence on my design for the particle system. For the effects I was looking for I didn't need to have different textures inside a particle emitter. Going forward I'm sure that will be an enhancement I will make. I also wanted to keep things simple as the tutorials were for beginners and I was learning at the same time
Apart from have a 64px limit and the texture needing to be square, point sprites have worked really well. As I developed the particle system I was originally using my own textures and switching to point sprites did make a significant improvement on performance. That said, I had not optimized the non point sprite approach as you have mentioned, so the speed increase may have been less if at all using that approach.
Having brought this up, I'd be interested to try a version of the particle system that uses the PVR/IVA approach and see what the performance is like. The particle system is very much stand alone at the moment with its own rendering code etc, so changing it should not be too hard. I'd need to find some time as the book is using all my spare capacity at the moment
but I think it would be an interesting exercise for the book as well.
If you have any other info or comments on this topic I'd be very interested to hear them