Batteries.... well, yeah, there's issues with batteries, just like there's issues with all the other power solutions out there.
The recent Volto release showed that batteries are not foolproof.
a) isolation of outputs, while theorhetically possible, is rarely done due to increased component count and cost.
b) due to (a) you can still get noise on daisychained lines.
c) Lithium cells still demonstrate 'memory' and 'soft' isuues, even tho they are a touch better than rechargeable gel-cells and NiCads. A battery's depth of recharge and lifespan can be decreased by leaving them on the charger longer than necessary.
d) and as seen on th eVolto, even tho the battery itself may be rated at 2 ampere/hours, that doesn't mean you can rely on it running a 500 mA device for 4 hours, trouble-free (Pedaltrain's online FAQ and owner's manual say as much).
Anyway, good luck to all you battery-users out there.