My biggest dream is a big epaper or pixel qi screen to do development on. The bazillion nits is killing my eyes...
My girlfriend is quite happy with her second-generation Paperlike Pro. There is apparently now a third generation[2] with higher resolution.
There are some disadvantages (of e-ink in general). It's not fast – the mouse cursor feels laggy, but typing is OK. You might have to tweak various appearance settings to make things look better in black and white – they have software to help with this for Windows, but not for Mac. Lastly, it's not particularly cheap.