It's the best duvet i've ever used. I have tried many different fillings and found that wool is by far the best. This duvet is of high quality. It regulates the temperature far better than anything else i've used resulting in better quality sleep. I think we are meant to be sleeping under wool.
I will give the top rating but there are a few small things that could be improved upon. The first issue is that the cotton cover is a little on the noisy side compared to most other duvets. It runs the slight risk of waking you up as you move about underneath the duvet.
I also agree with Peter from Dragon's Den. the duvet is a bit heavy. I bought a weight between lightweight and medium and still found it was a bit heavy.