Bad thing is - there wasn't any OST that I would buy in a heartbeat. There were some nice songs that fitted the drama, yet nothing as spectacular and powerful as, let's say, Chuno OST or Revenge of Gumiho OST. Oh yes, 2010 was a good year for dramas. Maybe last year of some quality in main 3 broadcasts' productions.
But if I had to pick up the best score - it would be NToG and What's Up! But the second drama started in December and ended in February, so it's not entirely 2011 one.