After a few days of burning in with pink noise, playing Skyrim, and listening to music, I can say I find these to be just as satisfying to my ear as the GR07, if not more. Burn-in doesn't seem to affect the SR850's much at all, but I'm still far from 100 hours.
1) While the SR850 and GR07 are similar in that both exhibit some sibilance, the SR850's sibilance is far more tamed and doesn't require me to EQ the hell out of it. That's easily my biggest gripe with the GR07. Even after extensive burn-in, without massive EQ-ing in the 6-8kHz region, they really hurt my ears. For the SR850's, flat EQ sounds just fine, though I prefer having the same region slightly toned down.
2) Sub-bass quality and quantity easily go to the GR07 but overall bass quantity and punch might go to the SR850. On tracks that don't have a sub-60Hz bass line, the SR850's bass is more satisfying to my ears. And I only have a few dubstep tracks that can actually bring out the sub-bass of the GR07.
3) SOUNDSTAGE! It's something that the GR07's get completely destroyed in, but that's not surprising considering I'm comparing tiny IEM's to semi-open cans. I can hear instrumental separation in my music that I have never heard before in my life. This also makes the SR850 amazing for positional audio in gaming. Just playing the circling helicopter demo in Creative's software suite is mind-blowing, and the same effect transfers into Skyrim.
I have very little experience with cans, but if the sound quality of these is "normal" for cans in the sub-$80 price range, I can't even imagine what to expect from $200+ cans.
My last comment is that the SR850 is probably the least comfortable headphone I've ever tried (I haven't tried many). While the automatic adjustment strap is a nice feature, the tightness of the headband gives me a headache after a short period of time. The squeeze also makes my ears hurt and sweat after a while. My cheapo $20 HD428's are much better in this regard. Can any owners comment on whether placing the SR850 on a wide object (like my BX5a monitor) for a long period of time will help ease the squeeze? Also, what about the AKG velour pads I've been reading about? Do they make these a lot more comfortable?