Hey ZappaMan.
I've had my KSE1500 for about 6 months, and have put a good amount of hours on them. They're my first foray into electrostatics of any kind. Prior to this I had Audeze iSine 20s, which were good but not great, before that Bose over-ears that were okay. I've heard some Audeze LCD4 headphones that were beyond my price range. They sounded good, but not as good as these KSE's. I find they flatter everything i listen to on them, and i listen to a lot of music new and old across most genres, flipping from Spotify to Youtube to vinyl to high quality vinyl rips to HD tracks purchases, and recently some R2R. Audiophile recordings are great on these of course, but I listen mainly to non-audiophile recordings. I'm not one to flip between multiple pairs of headphones or IEMS, based on what type of music they flatter, i think that's dealer-speak trying to hide design issues (just my opinion). Lean/little bass is one of the the few criticisms out there on the KSE, but there's actually plenty of deep, impactful bass. They're so fast and clean, that may be where folks say the bass is lean, compared a driver that rings out longer or is slow and clunky? Any type of music you like, you'll find yourself hearing WAY deeper into the song, not only because of how clean and fast they reproduce a musical signal and then its gone, but also due to the ~35dB isolation they provide, makes for an all-round quiet listening session. You could crank them to the max in the middle of church and no one would be the wiser. I listen mainly while i work my day job, sometimes i take them for a hike, to the grocery store, to the gym, even listen to them while driving. they're very detailed but not fatiguing, which is a problem for me because i'll end up turning the volume up as the day progresses, be careful if you like to listen loud, they want to be turned up loud.
I'm sure there are better IEMs out there, but not for the price. And i bought mine used for like $1,150 as opposed to $3k brand new. I think they compete/beat IEM's above their price range, especially when you factor in the cost of DAC/amp.
My criticism would be they don't necessarily slam the hardest, and i find myself wanting to turn them up loud for more slam.
Good luck.