We owned a 2009 W204 c180K pre facelift which didn't miss a beat.
Then a 2010 W164 ML300 CDI sport - owned 4 months (7000 miles) but the gearbox jerked terribly.
2011 W204 C220 CDI Sport Estate (facelift) didn't miss a beat for 3 years.
Now on a 2014 W212 E220 CDI Sport Estate, also perfect bar a bad DAB aerial, ride and comfort simply a different league to the C Class.
Yes, I have not heard any horror stories of the W204 or W212. They seem fine. The horror stories are all from the older cars from 1996/7 to 2006/7.