Got it as a company car at 55K km, later bought it. Kept it 8 years, then gave to my father, now happily driving it towards 400K km. (Old man had 5 R4s in his time so he's all grins now!)
By my limited experience (11 cars owned), R21 is easily the best car I've ever owned, especially for my below-average budget. Wins hands down when comfort points are added. Spacious family car with enough performance. A joy to drive. Reasonably, few can ask for more reliability than I got with it.
As a comment, R21 can be made to last 500K easily I believe, given attention to:
1) R21 engine head and gasket. It has a small design flaw (oil channels on the "outside"=wrong side at the back end of cylinder head). Do engine top and valves once and you're OK.
2) Annual care of brakes when driving in Scandinavian/winter conditions. All vehicles need special attention here, French, Italian, Spanish maybe a little more.
3) Sensible rust prevention measures, especially winter countries. Late 1980's Renaults are far better than their reputation in this sense, but need reasonable attention.
4) Normal maintenance, eg. all external subsystems that revolve every 100K to 250K km, as is necessary - like in any vehicle.
Level of "special R21 care" is still very reasonable for what you get in return! If R21 does not get its proper attention, at old age and mileage it becomes flawed with several problems that are partially reasons for "bad press".. - This is the difference of a French beauty to MB or other solid German "tanks" who go despite lack of service - but then, there is no joy as in Renaults !