For those of you having problems with power draw with the E17 and an iPad even when not in USB charging mode, why don't you just take a spare 10cent USB mini cable and a knife and cut out the 5v pin? Should force the E17 to run entirely on internal battery but still be able to transfer data over the 3.3v signal lines. I think the E17 even when not on USB charging mode draws enough power to run itself even when not charging (makes sense to do it that way if you have it docked in an E9, but I'm guessing the CCK USB port isn't putting out 500milliamps as per the USB specs)
Might be worth a try when I find the time - and yes, the iPad with CCK only allows for < 150 mA of current, quite a bit lower than the standard 500 mA USB spec. I still like the idea of a proper cable and/or battery powered USB hub, but something nice and clean that would still make the iPad a pretty decent 'portable' music player (when equipped with FLAC Player or VLC and loaded with well ripped FLAC content).