Got my K10's yesterday and thought I'd share some initial impressions. I couldn't resist putting them in almost as soon as I opened them when they were still cold and they obviously needed to warm up or the seal wasn't quite right (not likely as these aren't my first pair of CIEMs and the fit seems almost perfect), as the bass was almost non existent and they seemed very sibilant. I knew this wasn't right given what I already know about how they should sound, so I let them burn in a little while I made dinner and came back to them. When I tried them again I heard what everyone has been talking about with these.
First of all, the physical design is stunning. There is a reason people pay a premium for the Wizard designs and they are worth every penny; they are head and shoulders above every other IEM when it comes to design. Compared to my JH16's, they are also larger. The canal length is pretty much the same, however the housing is quite a bit bigger (they do need to house en extra 2 drivers per side) and they extend about 5-6mm further our from the ear. The contours of the acrylic housing were also much closer to that of the of my actual impressions whereas the JH16's were more rounded off, this might explain why the fit feels better despite being them being physically larger.
My first impressions were that they are very laid back, but I couldn't quite figure out whether this is a good or bad thing. They are very easy to listen to and generally this means rolled off highs and smeared details, however I remember someone in this thread saying when you really focus in on the music you will hear they are actually extremely detailed and I completely agree with this statement. They are very resolving but at the same time the layering is exceptional and each frequency just seems to flow into the next which I feel gives them that "laid back" sound.
The bass is wonderful. The quantity is perfect, but as others have said the main strength of the K10 is it's ability to choose when it can produce it rather than emphasising the bass across every track. My main over ear cans are the TH900's which are bass monsters and the K10's can just about match them in quantity with the right tracks and also have better balance across the mid-bass and sub-bass.
The treble is OK, I do feel it lacks a bit of sparkle but the extension is very good and they are not at all sibilant which is a major annoyance with a number of IEMs I've tried (although they will not hide poorly mastered recordings). Similar to the bass, if there is treble in the recording the K10's will replicate it with wonderful accuracy, however there is nothing exceptional to speak of here IMO.
My main criticism of the K10 so far is that they have a much narrower soundstage than other TOTL and even many cheaper IEM's. To be fair, I did my research and knew this would be that case before purchasing them, and I personally feel the trade off considering their technical prowess in every other aspect is a worthwhile one. That said, their imaging has been flawless so far, they just have a very "in your head" sound, even for an IEM.
I've saved the best for last, and that's the mids. Just......wow. I've fallen in love with the K10's mids already, they are better than anything else I have heard before from either a full size headphone or IEM (bar maybe the HE-560 but it's been over a year since I've listened to those). I don't even know what words I can use to describe them here. They are perfect. Perhaps this picture can convey my feelings about the K10's mids:
So do I feel they are worth the (not inconsiderable) price tag? Absolutely. For me, their biggest strength not any of what I have listed above, but their ability to be so versatile and perform so well across multiple vastly different genres. So far I have thrown at them: classical, hard rock, prog-rock, metal, blues, acoustic, pop, EDM, synthwave, soundtrack music and live recordings. With each genre they performed brilliantly and although they have some shortcomings with certain music (the boxy soundstage does not lend itself well to classical or live music), I never once felt the need to change to another headphone because the K10's would not be up to the task.
Do note that these impressions are based on only a few hours of listening so far. They also seem to be getting better the further in I get as I get more accustomed to their sound signature.