Early Japanese Reviewers have written the following:
1 early reviewer wrote: http://ayuchin.blog11.fc2.com/blog-entry-1186.html
The earpads are very comfortable and better than D1100. The headphone is much lighter than expected and faked me out, because the box was so heavy.
Upon first hearing it with minimal break-in, the tonal balance seems to be very similar to D1100 with the same kind of warm bass frequency. Not a significant jump from D1100 so far. Though the A100 does seem to have slightly more clarity than the D1100. In terms of soundstage, the A100 is very good and you can hear the position of the orchestral instruments very well. Instrument separation is very clear, but not necessarily mind-blowing. The sound signature itself is very gentle and not very forward or harsh. It doesn't have the airy and clean feel of open headphones but that is to be expected. The A100 has very strong bass, but it's coming from deep within the headphones and doesn't get in the way of the mids which are very vibrant. After listening to the A100 for 3 hours, I went back to the D1100 and found the D1100 to be lacking the lushness, clarity and instrument separation and sounding dry.
2nd early reviewer/test report: http://www.phileweb.com/ec/index.php?p=24010
They sound very lush and warm but well balanced. Very deep and powerful bass with vibrant mids. Soundstage is very good and the ear pads are amazing. The headband is the same as the D1100 but the overall headphone is very light and I like it. The bass drum has very big impact, but it's not loose and doesn't muddle the other frequencies. The highs and cymbal crashes sound very good and spread around the headphones very naturally. It doesn't sound harsh at all but is still very powerful and is well balanced. Female vocals sound very supple yet gentle and sound like you can feel it in your bones. Acapellas are very clear and engulfing and you can hear the voice separations very well. Hendrix guitar sounds are abundant but not overpowering or stiff...it just sounds natural with musical saturation. Bass doesn't sound linear, but instead is very smooth with supple grooviness. Great looks, quality and sound!
Hope these help!