Well, upload part (the one that involves USB cable) was fine and fast. Processing part was a bit on a slow side, but problems afterwards was what required restart of device. I don't know what caused device to start to behave, I just know that it was after I uploaded two dozens of books on device. It may be connected, but also maybe isn't.
And yes, I tried (as described in thread I mention and you also participated in that thread) with different USB cable, as I also thought that maybe I have faulty USB cable.
To sum it up, not all men (ops, H2Os) are made equal.
Lucky you, you got one without problems. I have one with mild bugs. They happen, device is not "rock solid", but nothing really major. It just annoys me. I'd like to have device more like yours, but I guess I'll need to live with one I have.
And yes, I think that it isn't so hard to believe that some device might have more problems than others.