I'm sending these back for a replacement pair, but I gave them a little ear time today since I can't get to the post office right away (seriously... why do they close at 5? We're all at work till 5!)
Early review: I like them a lot, they have a lot in common with the GR8 but maybe a tad more V shaped (a hair more bass and a decent amount more treble). I feel like the GR8 is "warm" to my ear because of a rolled-off treble, and the GR10 is "warm" to my ear because of a slightly heavier upper bass / lower mids. I EQed down the 220Hz band on my S9 and it started sounding just perfect to me, not warm at all but just right. There is a lovely delicacy about them and the texture of instruments and voices is beautiful. Like the GR8, I especially enjoy how they sound with strings. Excellent detail. Compared to the GR8s side by side they just have a more realistic sound. Outwardly the two IEMs are identical - cable, housing, tips. Just the color and the innards are different. The GR10s are substantially louder than the GR8s (~25% on the S9) but have about the same amount of hiss when plugged into a noisy source (my laptop).
I'm using them with modded Comply tips (trimmed to the same length as the Grado tips to keep the same wide-open sound tube and distance from the eardrum) - the Grado tips are great, but my ears won't tolerate silicone tips. It's really a shame because the ease of use with the included tips is incredible. You couldn't get a smoother insertion if you lubricated them, and they seal perfectly every time - no muss, no fuss.
I suspect I'll have a pair of lightly-used GR8s on the market in a few weeks