Mine is quite tough and I can certainly see some people finding them a bit much to live with. But being a light car does mean that the springs aren't actually very stiff, so the ride is reasonable when its all standard.
But as above, making sure the car hasn't been modified is probably your first check.
Then the little things, such as tyre pressures and making sure none of the wheels have lost their balance weights.
I had one of my front springs crack, it only lost about a third of a coil, but clearly something like that makes a big difference to the ride, so feel the full length of the springs and make sure they are all as they should be.
When you say on "smooth roads" then perhaps the car has had new rear dampers and still has old fronts, which can setup a horrible frequency when the car pitches. Mine did this when I fitted new rears, and the right wobble in a road surface would set it off. So I put new fronts on too and all was well.
Equally if its never had new dampers then £250 (all four from renault!) for parts and you could fit them yourself if you know how.