I still consider myself a KMC HM user, but I tried both the DS Matte and Eclipse sleeves as possible replacements once the whole KMC formula change thing happened (which I still don't really see, by the way - the newest ones I bought are still fine).

Eclipse sleeves had a weird issue with me where the inner KMC perfect fit sleeve started to pop out of the Eclipse sleeve, leaving the bottom of the card exposed to only the outer sleeve (so if anything got in, the card was exposed). The perfect fits I used were unchanged from the KMC Hyper Mattes I had them in before, they fit the cards perfectly, and that never happened before I tried the Eclipse.

DS: Mattes are definitely the preferred alternative to me - I bought a pack after the Eclipse sleeves had the perfect fit issue, which the DS sleeves do not have. Double-sleeving was a little more tedious with them, but they're much better than the Eclipse in my opinion.

The Eclipse sleeves are still decent, but my preferred sleeves go like this:

KMC Hyper Matte (I simply haven't had bad ones) >> DS Matte >> UP Eclipse

The DS Mattes have a great shuffle feel, they're built like tanks (as has always been the case with DS sleeves), and they keep the inner sleeves in place for me. The one thing Eclipse sleeves have going for them over anyone else is the black background on the card-facing side - this should definitely be something other sleeve manufacturer's take into account in the future.