Pros: Detailed treble, mid and bass. Great build quality. Replaceable cable. Very high isolating. Comes with hard carry case.
Cons: Fit a bit awkward until you get used to it. Not enough bass for a basshead.
Comfort & Fit
First thing to note, these earphones use balanced armature drivers rather than dynamic. Because of this getting a good seal is critical for the sound. Without a proper seal they sound tinny with no bass.
Straight out of the box the fit is awkward as you have to sit there fiddling with the memory wire that sits around the ear so that it sits firmly. Once the memory wire is shaped for your ear the fit becomes much easier and just a matter of sitting the cable over your ear and getting a good seal. I used the medium size silicone tips. The comply tips that come with it suck and ruin the sound. (Just my experience).
The build quality is excellent. The cable is strong, with a really good strain relief on the end where the jack is. The cables are detachable from the ear pieces and sit very securely in the socket. So secure that quite a bit of effort is required to take them out. You can be assured that the plugs will not wiggle around at all when you are wearing the earphones. The ear pieces themselves are very solid too. The cables are reasonably thick and finally the little tie-up thingie that comes up from the Y split doesn't press down on the cables it sits perfectly between them so it won't damage the cables like Hifiman RE-400.
When attaching the cables to the ear pieces you get a very tactile click to let you know it's locked into place.
The included hard carry case is extremely solid and feels like it could protect the earphones from a high amount of force.
The overall sound signature of the IM02 is quite balanced with a hint of warmth and light bass.
Highs are detailed and apparent, but never sibilant. I wouldn't call them overly smooth or rolled-off either, they are just a strike in between. Compared to the RE-400, the highs of the IM02 sound clearer and less veiled to me, which is to be expected as the RE-400 is warmer than the IM02. The treble extension did catch me by surprise. I tested the IM02 side by side with the Apple EarPods and the highs of the IM02 go so much further. Listening to Jetpacks Was Yes! by Periphery with the IM02 and the EarPods it became very apparent that the high vocals sound much "lower" on the EarPods, as if the person is singing with a deeper voice. Listening to a vocal heavy song will be very satisfying with IM02 as you will be able to hear the full extension of vocals that soar high.
Mids of the IM02 are clear. Listening to some Dream Theater to test the vocal strength of the IM02, I decided that the mids are definitely less warm than those on the RE-400, and clearer. Keep in mind that the IM02 are fairly neutral, but leaning on the side of warmth. The vocals of James LaBrie sounded very clear and definitely have some of the "intimate" sound of a smooth mid-centric earphone/headphone.
Bass sounds tight and punchy to me. Personally, I can't comment too much on bass, as I usually don't care about bass and I don't go out of my way to hear how the bass sounds. But overall it sounds tight and punchy to me, and definitely not boomy. Without a proper seal the bass is nonexistent.
Separation of these is quite great, and definitely better separating than the RE-400, which is no surprise as these are more neutral and less smooth than RE-400. The vocals are usually quite easily discernible from other mid-region elements of a song with the IM02. With the EarPods I find that vocals often sound like they are "combined" with the other mid-region sound in a song and this causes the vocals to sound pretty noisy. With the RE-400 this was still the case to a much lesser extent due to their warmer sound, but the separation on those was quite good. With the IM02 however the separation is definitely better than the RE-400 and now most vocals sound detached from the others instruments and never sound like they are "fused" to the other instruments.
For an average price of $200, these are definitely an excellent value. Sound quality is a noticeable step up from the RE-400, and build quality of these earphones is probably the best in the price range. (SE series from Shure use more impressive build materials but are renowned for point failures).