Pros: They've managed to capture the Grado headphone sound with these little babies.
Cons: Isolation. The tips are kind of small "than they should be," at least for some people.
Gear used for testing: iPod Video 80gb (5th gen, Rockbox) + Fiio E17
Test tracks: "Survival" by Muse, "Take the Power Back" by Rage Against the Machine, "Finally Free" by Dream Theater, "Hessian Peel" by Opeth, "Sacred Worlds" by Blind Guardian
Sound quality and signature: Not transparent. Presentation is upfront. But the amazing thing here is how they've managed to reproduce the Grado headphone sound with these small earphones (the shells are just as big as pills, probably smaller). This piece of work is a minified Grado RS1i. Of course it's not as airy as the RS1i, because IEM.
On lows, mids, and highs: The bass punch is similar to that of the RS1i. The mids and highs are amazing as well. Compared to my Westone 4R and my friend's AKG K3003, the GR10 is significantly brighter-sounding.
Comfort, build quality: Great for fun listening. Not very fatiguing. The 'phones are small but the build looks sturdy. Maybe other people will find the tips too small and may not seal it for them.
Overall: If you liked the Grado RS1i, you will like these as well. Small, compact, punchy, and bright. Grado-sounding in all aspects.