I have now done a little over 1000km on my MTB with the R180 hub and on my last ride a few days ago the ratchet (52T) stopped engaging... After a couple of minutes and pedalling backwards, it worked again and kept working for the remainder of the ride.
I took it apart when I got home and the grease looked kind of dirty, but nothing really bad. The teeth of the ratchet mechanism are damaged but after cleaning and re-greasing it seems to engage OK. I still have to try it on the road though.
I believe the damage will not really affect the working, but I will keep an eye out for further problems and I have another ratchet on hand to replace if needed.