I have a pair of the Campagnolo retrofriction levers (not for sale, and incomplete I think) but I prefer the Simplex ones.
The Simplex have a slight sloppiness to them. Usually when you change gear you move the lever past the correct point and then back a bit. The levers are a bit 'wobbley', so it auto corrects the gear change.
In contrast the Campagnolo have no give at all, so you have to move the lever back yourself, and also they are quite tight and more difficult to get moving.
Back to the bike; that has been my dream frame as long as I remember!
It's great to see a bike correctly sized, and without the bars, saddle and brake levers at weird angles. It really needs amberwall tyres though, those all black tyres really do look out of place.