Love the DS115J use it constantly to listen to music, watch videos and backup my macbook. The apps in iOS are great I just find it extremely useful. The user interface is brilliant also.
I have a WD passport usb hard drive plugged into it and it backs up on demand or on a weekly schedule.
Hey, thanks!
I just pulled the trigger on a ds115j and a 3tb wd red.
Was really thinking about whether it was worth spending more for a dual bay version, but then I would need to buy another disk, and an extra disk to back up to. It's a slippery slope that gets expensive quickly!
At the end if the day they all have the same functionality.
I think the 115j will do the job, if not, Ill live with it for a few years and get a ds217 or something to replace it.