I've had one for a few years and like it a lot. Excels in soundstage, air, and detail without tending to brightness or harshness. No hint of graniness anywhere - perfectly clean and smooth. Nice punchy, taut bass. Great for rock as well as classical. It has a nice clean neutral midrange, a touch of warmth there, but definitely not nearly as fleshy and fat/warm/lush a midrange as compared the Koetsu stone cartridges. In fact, if you jump from Koetsu to Shelter in quick succession, the latter can even seem a bit lean in the midrange. In some ways the bass seems tighter, faster, and punchier than a typical Koetsu stone. Maybe 20-40% of the time its flavor really strikes my fancy, and in those times I find my enjoyment of it pulls close to or even possibly even exceeds some of my better Koetsu stones (excepting my Blue Lace Diamond which stands alone as my very best) - especially on recordings that feel like they could use a slight shot of adrenaline when on the Koetsu. But the majority of the time, I at least slightly prefer the Koetsus (which I run on a Fidelity Research FR64S). Every once in a while I remember I should give the Harmony a listen after a period of laying fallow, and it can really surprise and thrill me. But no, it cannot match the Blue Lace - that one is special. Actually now that you remind me, I think I'd like to listen to my Harmony again some this weekend. It's not quite as "rolled off" up top as a Koetsu, but it also doesn't seem to suffer from the quintessential rising MC treble response that can be murder on my ears through my Tannoy's horn tweeters (at high listening levels).
If you've never heard it before and are getting malaise with your current rotation, it could provide a breath of fresh air. I also have its little sibling the Accord, and that has a warmer tone with a bit of the fatter midrange back (I think it's superbly balanced), but at the expense of some of the Harmony's detail. Both of these Shelters are a clear step up from the Ortofon Cadenza Bronze in detail and smoothness, though even that one is a pretty rockin' cartridge in its own right!
It works well with the Hashimoto HM-7 and Bob's Devices Sky 20 SUTs. Also seems to get on very well with the Clearaudio Universal arm, and VAC Renaissance phono stage. Unfortunately this line of Shelters hasn't gotten much attention or love from audiophiles.
BTW I still have the Koetsu SUT I got from you, and enjoy it very much with the Blue Lace - thank you!