Sorry, I haven't heard the GR07. But from what I've read they're studio monitors and thus the target group seems very different to me. In my book the IE80 are targeted at consumers who want a fun and engaging, but at the same time very high quality (high-end) IEM. The IE80's sound signature will most likely not appeal to analytical listeners, even though there's plenty of detail if you look for it. But for casual listening on the move they're almost perfect in my book, unless you need very high isolation. I prefer a little bit of ambience in order to catch what's going on around me, and the IE80 have just the right bass level and overall balance to drown out ambient noise and let me concentrate on my music, without isolating me completely from my surroundings. At home my preference is clearly for more analytical IEMs, but for on the go these hit a sweet spot with me.
I haven't experienced much change on my IE8 after the first few days. Of course I can't rule out very small, gradual long-time changes, but certainly nothing significant.