Of course the problems with bushwalking sleeping bags is that the synthetic fabric makes me sweat, the sweat soaks straight into the sleeping bag, and the sleeping bags are a pain to clean (I've done it a few times, but it's a major job).
Many people use a sleeping bag liner to avoid these problems (usually silk because it is light-weight and compresses well). I made myself one out of an old cotton sheet, many years ago. It worked well (although didn't compress as well as silk would have). However, I'm a restless sleeper, and found that the liner was too restrictive, and also got all twisted up, becoming quite uncomfortable. I had to revert to going without, and now I usually wear a flannelette shirt instead, which helps a bit.
I was thinking that maybe I could try full silk pyjamas (buy a silk liner, and ask my wife - who's very handy with sewing - to whip up some silk PJs). I would think they'd end up even smaller and lighter than a liner, and for somebody like me, they'd probably be a lot more comfortable. (Plus, I'd be the best dressed bushwalker at nights!

Does anyone ever take pyjamas bushwalking?
What do other people usually wear when sleeping in their sleeping bag? Nothing? Underwear? Shirt/Trousers? PJs? Silk Liner? PJs? Combination of these? Other?