We have had wool duverts for a good few years, and really like them.
They are heavier that the equivalent synthetic, feel more like a woolen blanket, but they do snuggle round you in a comforting manner.
I find much better temperature control - don't seem to get too hot or too cold, and never sweaty like synthetics.
Ours come as 200 and 300 gm, and can clip together for deep winter (I don't actually need both, even though I normally feel the cold).
Not as much of an allergy problem as down (possibly a problem if you are allergic to lanolin, but I don't know).
Highly recommended.