Well, one problem is that it's a modal interface without any indicator - I wouldn't personally mind having to wait 5 secs for the binary jump mode to finish but there's no visible (or audible?) way of knowing. A real undo would be limited to the availability of target keys (and their original meanings, which imo should not change for the sake of the binary jump mode being activated). So perhaps add Undo Last Skip to the context menu?
That could be an interesting option. I do think Thomas is right, maybe a true undo would be making it a bit complicated, but I can also see your point of why an undo would also be good. Perhaps you could have some subtle click sound play just to indicate when search mode had timed out, as five seconds isn't a long time to wait at all really.
