I believe my 520d M-Sport has the sports suspension, but it is nowhere near as "rock hard" as my previous 320d M-Sport. I took delivery of it with winter wheels & tyres fitted, but they're also run-flats, and overall I'd say the ride is quite acceptable.
2012 F10 520d M-Sport, Sport Auto, Imperial Blue, Black Dakota, Sun Prot Glass. V-spoke 281 Winter wheel package
Previous BMWs: 2009 E92 320d M-Sport, 2006 E92 335d SE, 2004 E60 530d ASE, 2000 E39 525d SE, 1997 E39 523i SE