The unit on ebay that this thread is about is the one that I was originally looking at. What I liked about it was the interchangability (Is that a word?!?!) of all the bits to give different looking units, plus the fact that it is small (states that it is the size of a cigarette- both in length and diameter).
However, after doing some research on here, I am now concerned about it as it would appear that on the smaller units (and this seems to be about the smallest I've seen) there is an issue over the batteries only having a short usable time between charges, meaning that you would need loads of them to make sure you didn't run out of power.
The other reason I am now moving away from this particular e-cig is because I would like one that I could use a USB passthrough with, and I doubt that there would be a compatible unit for it.
Incidentally, I emailed the seller a couple of questions to this seller about the battery and I haven't received a reply during the last day and a half... although the seller does seem to have pretty good feedback.