IIRC there was an anti-bacterial boom in Japan several years ago... when I first started surfing the web (1996) there was a kenwood walkman with "anti-virus" printed on
Nowdays it's no longer a big deal (from my understanding)... but
First off, H.D.E.S. is tuned to emphasize the lows and the highs relatively more, as opposed to the original ATRAC idea of completely following the ear's masking curve (most sensitive to mids/less sensitive to lows and highs). I think that's what makes the outcome less closed-in.
I'm sure someone can explain it better, but:
Within ATRAC the incoming signal is "classified" in a number of ways, one of them is a pick between "long" and "short" time-domain windows. The long mode is used more, as it provides good solution. But with attack signals (loud sound that suddenly rises out of silence) the long mode will induce some quantization noise, or "pre-echo" noise that wasn't in the source signal.
What H.D.E.S. does is to make more use of the short mode to minimize the pre-echo. On the MR200, HDES only kicks in with the AC adaptor, and the display will say "digital HDES" or "analog HDES" when it's in action. On the MR220 it functions even on the gumstick.
The MR250 seems more like a facelift of the MR220 (all jacks in the same place), but who am I to complain, I like the design too
P.S. that AVwatch thing isn't a press release... it's a news website.