Initial impressions: I'll try to be careful with how I phrase things, as some people may have their purchasing decisions influenced by what I put down.
My initial impression at the shop was that the Hemp was awful. The demo setup had a "midrange" row of GH4/RS1e/PS500e and Hemp together. The GH4 was the best of the bunch, while the Hemp to me sounded the worst by far. Against the "Prestige Series" row, I thought the Hemp sounded worse than the SR60e. I would take my $40 KSC35 over the Hemp. There's no treble energy at all, and it's almost as if Grado made a headphone with the "Sennheiser veil". It was indeed a Grado for people who don't like Grado. I thought maybe that's why there's been so much praise for it.
So why did I end up buying it? First off, it's in high demand, so if needed, I could sell it off quickly and recoup most, if not all of my money. Second, I asked the shop if I could try the Hemp with G pads. Contrary to what some people reported, I felt the G pads on the Hemp made it significantly better. I couldn't say if they were better than the GH4, as I didn't have time to put the G pads on the GH4 for an apples-to-apples comparison. Based on the hopeful quick impression with the G pad, I bought it, hoping that I could EQ down the apparent treble spike that was added with the G pads.
I'm now about 20 minutes into listening on the Hemp with G pads on my own rig. Hm... this is strange. On my rig, the the treble sizzle is more prominent. I'm not a huge believer in headphone burn-in, but maybe the headphone needs a bit of time to settle? I also hear a bit of a mids suckout as johanchandy reported when he tried the G pads with the Hemp.
Full review will come in a few days. I feel that ultimately I will give the Hemp a positive review, but I'm not sure if it's a giant killer, as right now I'd recommend the GH4 over it, if you can still find one.