Our girls are in a king bed with us, with a crib sidecarred to the side, but no one's actually sleeping in the crib yet! We put the crib there because that's how we slept with DS (now 3). Now with the twins, we've pushed the bed againt the wall and actually have the girls on that side next to the wall, vs being in the crib. They sleep next to each other, perpendicular to the wall and to me. So their heads are by the wall, and their feet are at my side. Then when they stir, I just move to nurse whoever stirs, and either go back to my original spot, or fall asleep with one nursing. I basically just shuffle to whoever needs to nurse. Sounds a bit crazy, I know, but it works for us! I find that if I sleep with a babe on either side of me, they always skootch closer and closer to me in the night, so I end up squished in between them and then can't roll over to nurse the other one! Then I can't get back to sleep cause I'm too aware of which girl is potentially going to get squashed when I roll over to feed her! I'm not sure how long our current configuration will work, not sure if eventually one or both will end up in the crib. We'll see!!
Oh, and when DS was in the crib, I was also worried about the part of the bed that was open (without the crib there) and ended up piling a whole bunch of pillows on the floor there. Sure enough, DS crawled his way out after a nap once, tumbled off the bed, and was saved when he landed on the pillow mound!
ETA: I think one of the reasons our configuration works, is because I'm really short, so I don't take up the whole bed when I lie the other way!!