Been used TASCAM DR-40 last year and it was just fine, without any issues. But when I bought this one, and it's a new model (DR-40X) of the same product, I found out (and not only me), that it's not working (not turning on) with batteries included or any other ones. It only works when plugged-in with USB cable, for me it's not right and I don't want to use this product only with USB cable.
Such a shame TASCAM made new model like that, they've changed only USB port from mini-USB to micro-USB and changed the screen color, but ruined very good product it was before. And also now they're not supplying this item with SD-card like it was with DR-40 model.
Overall, recording sound is very good. But ... it's not portable.