You might want to change the title of the thread so that it's more informative to more people, like "Earin --- Bluetooth IEMs on Kickstarter". I'm sure many people have the same questions you do.
In terms of Bluetooth audio support, it supports A2DP Apt-X, so it will do lossless CD audio.
Is it going to delivery really good sound quality?
Who knows. The electronics are tiny, and so the D/A conversion will have its limitations --- I'm going to guess it'll do a maximum of CD quality dynamic range, but it'll probably be worse.
In terms of the sound itself, they are using Knowles SR drivers. Products in the past have used the SR, and they sounded okay, not great, not terrible (referring to the first generation SR6438NWS). However, there is a second generation SR driver, the SR-31843-000:
This one has a balanced sound profile, and doesn't sound too terrible.
All SR drivers tend to sound a little warm, a little indistinct.
However, it's up to them to figure out how to best use the driver.
The curve you see there is idealized by Knowles themselves.
From photos I've seen on earin's Facebook page, they seem to be getting technical support from Knowles, so sound quality-wise they shouldn't be too shabby.
I don't think this should be about sound quality, however. It should be about the ease of not needing any wires when moving around and listening to music.
There's an ergonomic hurdle to the earin, however. It looks a little fat, and unless you have large ears, they actually seem like they might fall out easily.
Yes, they have a concha lock thing to help keep things in place, but I don't think people want to have to deal with that.
They could've made the structure a little thinner and made it insert into the ears better, but I guess they wanted a more traditional structure so that the mainstream would be more receptive to it. After all, a lot of people are still wary of sticking IEMs deep into their ears, and not used to the "invasiveness".