Just for the sake of completeness, several months ago, after first receiving my X5, I reported a click that seemed to happen between gapless tracks, and only on the X5. Several iterations of the firmware later, that click disappeared, except on one single track -- the click was prominent on the X5 but wasn't on the CD. This is music that I mastered at 96k/32-bit and had downsampled to 96k/24-bit for the X5. The CD, of course, was 44.1K/16-bit. I was afraid I might have had a defective X5, but I'd been too busy to do anything more than mention it here, and in some PMs with Joe. Well, tonight I couldn't sleep so I finally pulled up the session from which the master was made and saw a spike to max volume on one track right where I'd hear the click (the selection has 120 tracks, so I might be excused for not having caught it sooner). Adjusting the level on the master didn't change it -- apparently I had tracked the original recording that way (it was a drum track so, perhaps, not surprising, but it could also have been a power spike or EMF). I edited out the single cycle that had the spike and, now, the master plays perfectly on the X5 -- no click.
Not news of any kind but, as I said, I wanted to be complete and don't want anyone to think there is any problem with the X5 in this regard. However, it's worth emphasizing that a hi-res audio file will only be as good as the master; poorly mastered audio may actually sound worse in hi-res as in this instance -- the extra 8-bits of dynamic range for hi-res resulted in the music masking the click on the CD, whereas the click stood out quite clearly on the X5.