Thing is, we were on a flight to Ireland. It was not appreciated. I think this is basically how you were raised. My parents didn't consider it a horrible word, so I didn't either. I kinda learned that day, but it still carries much less weight than 'godverdomme'.
Not being Irish, I'd never heard of it until I first saw Father Ted [0], and was initially shocked at the characters uttering what I assumed was a dialectical variant of "fuck" every five minutes.
To anyone wishing to swear in English (as a second language), "feck" is a very good choice to try and make as your instinctive choice. It really is not offensive - I suspect it might be based on the word feckless, rather than fuck but then I'm English and not Irish and have no idea. Perhaps it is an Anglicization of a Gaelic word.