I use a down bag and usually can keep it dry.  It is packed in a water PROOF pack and my OCD kicks in when it comes to guarding that the sleeping bag stays dry.  It is generally the last thing into the pack and the first thing out; I hang it up to air out every morning and evening that it is nice enough and there is a little time before the sun goes down (once the sun goes down it starts to get damper instead of drier).