I've rested in the BMBH several times, napped a few times, and on 22 Dec spent my first full night sleeping in it. It's hands-down the flattest hammock I've slept in, at least from head to foot. Very easy to sleep on my side, and I spent most of the ~6 hrs in the hammock doing just that. My wife has immediately discounted every other hammock she's tried after about a minute...the BMBH is the only one she's said she'll try for a night, simply b/c of this flatness.
I did get that "shoulder roll" that folks complain about with the BMBH, though. This is something that never really bothered me while napping b/c I wasn't in there long enough. I slept so long on my side that my shoulder started hurting, so I rolled onto my back...but that wasn't comfortable b/c of the shoulder roll. I could accommodate part of it by putting my hands straight down and laying them on top of my body...but that didn't stretch my shoulder like I needed it to. If it were warmer I would have put my arms over my head, which has been comfortable while napping, but not so comfortable at 21F. Or slept on my stomach...again, pretty comfortable while resting but I don't want to breathe into the underquilt when it's cold. So I ended up staying on my side and dealing with the ache. For reference, I wear a 42-44" chest size.
I also like to pull my legs up when I'm sleeping on my side. Not quite fetal but almost...this helps me stretch my back out. The BMBH is too tight along the sides to do that. Again, this wasn't an issue while napping but over several hours I kept trying to curl up in my sleep and couldn't. This is just a peculiarity of how I sleep and may not affect others.
I haven't tested it yet with a pad inside, so that may open it up more and make it much more comfortable on my shoulders. Maybe use a Downmat 7 underneath and the MWUQ on top? That's edging up the weight but may be the most comfortable combination I've used...have to play around with that.
So like everything else, I'll give it a couple more tries before I make up my mind. And I'll have to see what my wife says b/c it's her hammock anyway. (At least I tell her that's why I bought it... )