Has anyone had any experiences having fitted a K&N filter to a 4.2S/C.

Do they make any difference?

Best stick with the original filter, the K&N requires oiling and the oil goes onto the MAF sensor

Best stick with the original filter, the K&N requires oiling and the oil goes onto the MAF sensor and boogers it up

Don't notice any difference with mine in, for me it was the convenience of having a filter that I can clean when needed (especially after Harmatan). Not seen any MAF issues sofar due to the filter. MY 2010 5.0 SC Galway green and sand interior!!
Have the Faultmate MSV2 Extreme to be tinkering with the settings etc. !!

I would stay away from it just because of its filtering ability. It allows more air into the engine because its less dense than a regular filter. What makes it effective at all is the oil, but once it has a few miles on it the oil isn't going to capture the dirt and it will be in your engine. For a fair weather weekend car or racecar K&N's are great but for an off-roader or DD don't do it! Especially with the supercharger, a little dirt will destroy the seals and you'll end up way down on power.

I have seen the raging war on the internet between pro and con of the paper vs. non paper filters. The main reason for me to switch to K&N was very simple, paper filters here are more expensive (than the K&N I bought in Europe) and flying them (paper filters) in every 10,000 to 15,000 kms seems a bit ridiculous. Whether they are better or not, I don't know based on the information that I have read sofar.

Normally I would stay with paper filters when they are cheap and easy to get hold of and also I don't like to regularly clean and re-oil the K&N (type) filter. However if you don't have a choice then I'd say go for the filter that fits, anything is better than no filter  MY 2010 5.0 SC Galway green and sand interior!!
Have the Faultmate MSV2 Extreme to be tinkering with the settings etc. !!

I agree that any filter is better than none. There isnt much to debate on which filters better and which flows better. Obviously to flow better a filter has to have larger passages with less restriction.

At at a job I had in high school working for an automotive speed shop we did testing using one of the tabletop demo flow boxes. on the inlet it had a changeable filter, the outlet was a vertical tube with a pingpong ball. in the box there was a fan pulling air through the filter and pushing it out the exhaust. We took the test a step further and started putting dust into the inlet. At the beginning the k&n stopped a decent amount of dirt but shortly started letting some through. The paper filter didn't flow as well but never let anything through that we could see. lastly we put a green brand racing filter in. It flowed much better than the k&n but barely stopped any dirt.

I'm not trying to start a debate or say anyone is wrong. My experience has proven the pros and cons. Obviously if that's all you can get or is the most reasonable cost wise go for it. Just clean it as often as possible so you can minimize the chance of dirt entering your engine.