its hit or miss, in the snow 2 weeks ago when my flight was cancelled they were on form and sorted everything as best as they could.
When my baggage didn't make a connection through Schiphol (both KLM flights) earlier in the year useless wouldn't even begin to describe their customer service.
I have found that once you have completed your trip and are trying to complain by email or telephone you may as well give up as they aren't going to help.