I ordered this in white in a medium...I'm a 36C now (1 week away from babytime!).  It was too short from front to back, and rode up so the elastic band was on the bottom of my breasts, not on my ribcage like a bra should fit.  I'm exchanging for a large, hope that fits!
Overall, I can see how this will be very comfortable for sleeping/nursing at night.  The fabric is very thin, so it won't be something you can wear around the house...but it is nice soft fabric, which will be light and breathable for sleeping in the summer.
I would recommend a size bigger than you measure, just because it is cotton and will shrink.  Overall, excited to get the correct size and start using this bra.