I have been in wet, rainy, snowy, miserable, blizzardy, sopping, darn near hurricane, and other such conditions more than I care to think about in the backcountry. For many many days. With a down bag - repeatedly.

Don't get it wet.

If you can handle that, there's nothing at all wrong with it,
if you can keep them mostly dry, they work better than synthetic and are lighter.

If you do believe it might get totally soaked, go synthetic.

Many people here will patronize newbies and say "I don't belive you will keep it dry so I'll reccomend you take synthetic until you gain experience" - it's a safe bet, but I believe is something that if you are careful, you can mitigate by other factors. (like not getting it wet, having a bailout plan, etc.)

Most (not all) experienced people here will probably admit they usually use a down bag for most of their trips.