I also bought one, hope it is sort of worth the 200Eur i paid in the end.
I guess it will be good enough for what i need a portable scope for (as im getting rid of that not really portable TDS3014 w/battery now, before it gets entirely worthless).
It probably will be good enough to look at some rotary encoder signals, triac switching and signals like that.
Yes, both channels DO share the same common! It is not grounded (on battery, and with no usb connected). So if one decides to float the common, it would be a really good idea to insulate all other connectors...
Isolated channel scopes are quite a different price class, and i would not buy anything chinese there, as most applications that require isolated channels will deal with high energy. Rather go for a R+S RTH (the one that sucks by far the least, compared to fluke, tek or agisight) here.