Many cyclists might take a look at the Randonneur shape, sniff, and dismiss it as too retro, given the bewildering handlebar choice on offer. True, fashion changed in favour of the Mayes design in the post-war period (straight from the centre, evolving into a gradual curve), but in line with their name - randonneurs being long, non-competitive rides like audaxes - they are well suited to long rides and rougher surfaces. Their shape allows comfortable positioning on the drops or bends without needing to turn the wrists.
The polished finish is very good for an inexpensive bar and their 45cm width offers phenomenal comfort and control. Some might sneer at the absence of cable recesses and the 25.4mm clamp diameter, but these are easily overcome without resorting to non-aero levers and quill stems (although they would be ideal on a period bike for this very reason). I dislike shims as an engineering solution, so I opted to run the bars on my mountain bike-based 'crosser with a modern Ahead-style stem. Their width might be a problem for those seeking to squeeze through the narrowest gaps around town, but they really come into their own when pulling a trailer or green laning, offering welcome extra leverage and stability.
Held in a death grip with all my weight against them I could detect some nominal flex, which was actually welcome on rougher surfaces and shouldn't be a problem unless you happen to be 18 stone with hands like shovels.