I had this car, fully specced 2017 CLA 45 AMG and I wasn't satisfied with it. Built quality was bad, plenty of rattling in the interior (passenger's seat, passenger's doors, roof, central display...), small rust spots appeared on the fenders and trunk lid after 5 years despite regular washing and maintenance.
Performance wise it was bad - throttle response was beyond terrible even in Sport+ mode, handling like a pig on skates compared to Audi RS3 or BMW M340i, both of which I drove.
Measured acceleration (100 octane EU fuel) was:
0-100 km/h: 4,5 s
100-200 km/h: 12,8 s
In street race my former CLA 45 AMG (381 PS) was easily beaten by BMW 335d E90 stage 1 (340 PS), beaten by stock BMW M340i (374PS), beaten by stock Audi RS3 (367 PS). Otherwise two official MB service centers found no issues with the car...