I sleep in the Bravado Bodysilk Seamless. It's seems as comfortable as I can find, given I hate sleeping in a bra. I also use them a lot for everyday wear.
Are you looking for bras to sleep in or just regular nursing bras? For regular, I have the bravado bodysilk as well. They were pricy, but they're really comfortable. I also have a couple from Target. I don't like them as well, but they work just fine.
I didn't care for the sleep bras. The ones I had just pulled down over the shoulder and it never seemed very convenient to me. I just bought a couple of nursing tanks from target and I slept in those every night.