A word of warning to anyone considering this NAS:
As already pointed out by inkytires, the power-management features are badly implemented.
The NAS has a power switch with positions: auto/on/off. Choosing "auto" means that the NAS turns itself off (power down NAS, HDD) unless it is kept awake by an instance of the NASNavigator-software. It is a bonus that the NAS has wake-on-lan (WOL) capability, but as it is, the feature is not useful for equipment where NASNavigator (or other WOL-script?) cannot be installed.
I was aware of this limitation before buying this NAS, but noticed from the product manual that there is an option in the browser interface to enable "HDD spindown" (standby power-mode). So, my plan was to leave the unit "on" 24/7 and use this power-saving feature.
However, at least for my unit (1.0TB, Nov 2009, "HD103SI"-HDD inside, stock firmware 1.10) "HDD spindown" does not work. The drive is never spun down, even with all services shut down and LAN cable unplugged. This problem has been mentioned in the Buffalo forums, but there is no indication that it is going to/can be fixed. "HD103SI" probably refers to the Samsung HDD which has been found problematic also in Synology NASes (HDD hibernation does not work, in Synology's language).
Overall, the LS-XHL seems fine, but I felt mislead by Buffalo, and will definitely consider twice next time.