He's been in bed with us both since birth. He sleeps on both sides of me, depending on which side we're nursing on. DH keeps him in bed on one side, his sidecar is on the other. If DH is compromised in any way (he occasionally takes a melatonin to help him get to sleep, he gets restless legs), I just keep baby on the sidecar side for that night (sit up to nurse the off-side, if I need to).
However, DS is snuggled RIGHT up on me (his preference, and I don't move in my sleep anymore) and there's at least a foot between him and DH. DH can be a heavier sleeper, but since having DS I'm definitely not, and DH would literally have to roll on top of ME to be on DS, so I'm okay with this arrangement.
We've had the duvet since day one, too; DH uses his side normally, my side only gets pulled up to the waist, and I cover my shoulders & DS with one of his light fleece blankets.
I worry more about him getting smothered by my boob than I do about the blankets or DH. =S