I don't think you guys realise how complex it becomes to implement image atlas in a particle system that advanced as the one i have (think different pixel formats and sprite resolutions and include the per-gpu image size limit), and pretty soon managing all that becomes harder and the speed increase ends up being neglectible.

Do not say that the design is wrong, i was just pointing out that sometimes the VBOs don't go well with a existing system that was made to be something more than just sparks.