the kickflash stores a kickstart image in it, plus whatever other drivers u need (like the poseidon stack) and the boingbag updates you want. in a way it builds a super-kickstart up to 1MB. then when the amiga powers, it reads that instead of the ks-roms, and u have a nice single boot machine with drivers on boot time, so u can boot from usb or use a usb mouse.
edit: all work from cold boot, u can use it in whatever wb u want and the OS4 means that when the software only OS4 ks update gets released, u can store it in the kickflash and not softkick like the BB updates.