The goal is to have a flash drive that can be plugged into any machine I run into and boots into my chosen desktop, with my chosen software installed and available. That way I can carry my computing experience with me, and the only differences between different machine experiences are hardware limitations on some older machines. A unified experience on multiple computers, priceless.

Then, in addition, Porteus-like software injection allows me to add and subtract functionality on the fly, keeping the OS as svelte and fast as possible by only having software that I need for the task at hand. It really is quite amazing.