So Eke was kind enough to send me his set of GR07 MK2's for direct comparison with my MK1 pair. From what I remember reading prior to receiving them, things I expected to hear were very small, subtle differences between the older and new pairs. This was not at all what I found. I don't recall reading what was done in tweaking the driver (or if anything was done at all), since I haven't kept up with the thread very much unfortunately-- so bear with me on this brief comparo.
I listened to Eke's pair first as soon as the package arrived. I'd been enjoying my TG!334's prior to this, so when I put the MK2's in, I was actually quite surprised at how enjoyable they were immediately after the 334's. I didn't remember the MK1's being like this right after the Fitears. So I went through several of my favorite test tracks, and I found with every one they just handle the whole dynamic range so beautifully. Lows are really deep yet controlled, midrange very full and properly placed (neither recessed, nor overly forward), and highs very clear and very much extended.
After this session, I got out my MK1 set, queued up the same tracks, and was pretty stunned at the differences. This wasn't subtleties at all. In comparison, the MK1's show a much more choked in and one-dimensional soundstage, and the midrange is noticeably thinner (almost more of a sterile feeling to this area) and pulled back. Treble seems about the same, with the newer version possibly having a touch less 'hotness' up top. Bass is perhaps a touch less extended on the MK1's too. So, overall, these areas combined really make for a hugely improved earphone with the MK2.
So what I'm left to believe is either they made quite a few changes to the driver to gain this amount of benefit, or my pair is not a prime example of what the MK1 is capable of. And I feel that what I hear between the two is significantly more than can be explained by improving the cable. Having heard the MK2, I feel it is even more of a huge value in the IEM world, and I will be ordering a pair even when I have the MK1's.
Here are some images to compare. The molded parts on the MK2's look a touch blacker, and as is plainly noticeable the cable coating is more of a copper color. And the silver strands are hinted at barely through the almost opaque coating.