Well - been doing some more listening and recording (of the headphone-out) tests... and the Vibez does suffer from exactly the same problem as the Karma after all, although to a slightly lesser extent in one way, but a more discernible way in another. With all material, even those which plays without a human-perceptible gap while buffer refresh is happening, the HDD noise does bleed into the headphone socket. This is something that I've not noticed to the same degree with any player bar the Karma / Vibez.
I'm still having specific FLAC problems, but leaving those aside going to high-bitrate MP3's, the spinup does introduce a blip (slightly less noticeable than the Karma), and while the HDD is spinning it does distort the music (more noticeable than the Karma). When there's a fundamental issue like this, even though the Vibez and the Karma before it are very competent players, the fact that you can get better nowadays and that it has defects like this hamstrings me from giving out any recommendations for it based on SQ.
Given my Karmic experiences, I refuse to believe this is a coincident at this moment, although I have requested an exchange from the vendor.
The better and/or more isolating your phones are (and the better your hearing is of course), the more you'll notice this. Whether it's an issue for you is something you'll have to decide for yourself. It is an issue for me. The rocker wheel is also fast becoming a minor annoyance, especially the ill-thought-out centre button.
It's a generally respectable player but the more I look at it based on it's actual performance, the more my response to the hype building up around it on Head-Fi would be "... yes? And?".