I got the Aeon Opens two days ago; here's some impressions:
Note: not burned in, source is Grace m9XX and Chord Mojo.
Bass: Definitely north of neutral to my ears. Good impact, making music more fun to listen to, without being overbearing nor tasteless. Though sometimes I feel like instruments such as the cello stand out a bit too much in the mix at times when listening to orchestral pieces, though that may just be a sound adjustment issue. On the other hand, kick drums are a joy to listen to with these
Mids: Rich, warm, present. A little veiled with the white tuning filters, masking some of the overtones and nuances with respect to vocals and some instruments like violin, but not a big deal; it's easy to adjust to.
Treble: Lacking some air, but well extended to my ears; cymbals and such crash with authority. A bit of sibilance at times with poorer recordings but not the worst I've heard. Maybe a bit too hot for me with the black tuning filters... I'm still experimenting.
Soundstage & Imaging: Narrow, but adequate depth to my ears. Imaging and separation are decent I suppose. I've been pretty spoiled by the HD800, so nothing is really going to compare in this category.
Attack/Impact: Definitely punchy and dynamic. High musical engagement factor. Does well with crescendos and climaxes.
Overall, I really like them despite its flaws. Worth the money for sure.
Pros: Cohesive. Smooth yet punchy. Fun and engaging.
Cons: Soundstage. Mids a teeny bit veiled. Some sibilance.