Czech Airlines are changing their rules of the OK PLUS program, so this might be a valuable information for all those who consider making the switch:
Beginning the 2015 summer season, you will need much more miles to qualify for a silver (25K, was 15) or Gold (50k, was 30) card. The number of legs increases (15 vs. 30) as well, but mainly, YOU HAVE TO FLY SIX CSA FLIGHTS in order to qualify for the gold card.
The new rules are already posted, no validity on them but the old rules are already gone.