We'll obviously hold off with our final yay or nay until we can stress test the bits off it to test how it copes with load, efficiency, PFC and noise levels in comparison to other PSUs. We did test it for a short while with a Core i7 system and two GeForce GTX 280 in SLI, the unit remained cool and very quiet, however even that high end PC won't seriously stretch an 850W PSU.
From the outside, it looks like Seasonic has done everything right - a variety of modular cable lengths with good connector choices and lower resistance, thicker cabling where it matters, a fantastic fan and 80Plus Silver certification. If we nit-pick, then the braiding isn't perfect and we'd like to have seen a second 4+4-pin EPS12V instead of just a 4-pin, but other than that we're finding it hard to give fault. I suppose it's a little unspectacular on the surface, but then it's no different from an Antec Signature or OCZ EliteXStream - it's what is inside that counts anyway.