I have the Duos for over 2 years, and I am very satisfied with them. The L/R balance from the Duos is vital info. Initially, I thought my right leg was the strongest, but the Duos indicated either neutrality or left left is stronger. Also the power is more accurate with the Duos. Not that all this is going to make me faster, but I like to records numbers.
The one problem I had was that unclipping was very hard. I could only unclip with my leg at 6 o'clock position, and with a lot of effort even at the lowest setting. This was a little tricky at stop signs or unexpected stops. After contacting the maker they said the springs would "soften up" which they didn't. Unclipping became easier as the cleat wore, but when I replaced them with new ones the problem returned. I decided to lubricate the side sliding surfaces of the pedals, and that solved the problem.
My son recently bought Duos, after convincing him not to buy the Unos. He also is very happy with them, and didn't have the unclipping problem I had.