The Met continues to arrest people for swearing at police as they rejected the ruling. I know that Police Scotland continue to arrest people for swearing at police but I'm not sure how/if it has affected forces in England and Wales. At the time it was reported that the precedent could likely quash any future charges in similar circumstances.
There's 2011 advice provided to the Met which says that courts are unlikely to convict because officers are assumed to be robust: http://www.bbc.co.uk/news/magazine-15816761
It's probably a bad idea to direct insults at officers (because no-one likes being called a fucking facist wanker) and results will vary by location.
I'm not sure, but I think that after the first time the officer should say "don't use that language at me" and therefore probably tells the citizen that they are causing harassment and distress. Then if they continue to do it, after the warning, it becomes an offence. So perhaps it should be "continues to use offensive language after a warning about the language has been given".