Over the last 2 months I have been experimenting with getting rid of my duvet for sleeping. I'd been thinking about it for a while and decided to trial sleeping with a blanket. A few days ago I deemed the experiment a success and got rid of my duvet completely.
One of the main reasons was cleanliness. I find duvets notoriously hard to wash, so it hardly ever was. It would also mean doing a separate wash, as duvets are puffy and don't fit in with other laundry. A blanket means I can throw it in with any other washing I'm doing so it's not an issue.
I have taken up the habit of folding away my bedding and lifting my bed up, to create more space in my room. A duvet is much larger than a blanket so it takes up more space.
Funnily enough, I believe in comparison to duvets, blankets are less of a "comfort blanket" for staying in bed hours after waking up. I am less inclined to surround myself and lie there for hours on end.
Apparently duvets only became popular in the 1960s, marketed as a convenience product against fitted sheets. I can see why but as mentioned, I fold my bedding away on the side.
Of course I'm not going to deprive myself of quality sleep so I would revert if I felt my sleep quality had decreased. Subjectively at least, I don't believe the change has affected anything, at least nothing more than external stimuli (such as noise) does.
I guess the only downside I've experienced is that you are more susceptible to room temperature. Duvets are pretty good at trapping heat in. However, we've just come out of the coldest period and with the central heating on high enough to keep the house warm in the day, I didn't experience too many problems.
In conclusion, experiment success.