Actually the battery option doesn't interest me at all. The attractions for me are are
1: It works as a stereo speaker system for my PC (and pretty HQ from the reviews I've seen)
2: Its a recording interface for my guitar, bass & keyboard
3: I can have stereo playback of my tracks and jam along (either through USB or AUX in)
4: I get to play the guitar with stereo effects
5: The sound quality seems to be very good all around.
6: The interface seems pretty basic - don't have to scroll through and edit a tone of presents.
7: It portable
8: It looks kinda cool and different.

I currently have a Fender Mustang Amp which is great but only acts as a recording interface, it doesn't do playback so monitoring yourself as you play along to track is very difficult. If also needs a lot of tweaking to get a decent sound, especially on the higher gain models. The sound of my ipod through the Aux In is pretty poor and mono. So for me the Yamaha ticks a lot more boxes overall.