I have the XP18000 and use it to power a DR680+SD USBPre 2. As the others have noted, the power button is a bit of a nuisance. I opened mine up to see how many and what voltage of cells it uses and predictably there were 3 x 3.7v, giving a total capacity of ~67 watt hours. This is quite a bit below other similarly priced products out there, but the upside is a reputable brand name and hopefully higher quality control levels.
My only other problem with it is apparent power drain even after the power has been switched off. It will be dead overnight if I don't disconnect every device from it. It needs a hardwired power bypass switch inline for it to be foolproof.