Hi, I do not have a lot of time now. I write some info:

when host mode with boost is enabled, then n900 supply voltage boost - this is needed if you do not have external power supply for usb device. host mode with charging is host mode without boost. in this mode n900 does not supply voltage, so external supply (from hub) is needed. Also in this mode can be battery charged (it will charge battery automatically if power is detected).

CSSU testing is needed because it has updated ke-recv which automount usb disks. Reason is that CSSU is right place where can be system packages updated (because nokia never release updated system packages)

blue led light when boost mode (which drain battery) is activated. you can edit led pattern in control panel with extras package led-pattern-editor

also vote for package mceledpattern which is needed for registring boost pattern in mce.

Estel, this is same implementation of usb host mode as in hen. Only battery charging & boost is implemented in kernel and musb export speed of connected usb device to sysfs.