I personally prefer "Holy Spirit", because with what wee little bit of Latin I know, 'spirit' comes from the same root as 'inspire', and basically means 'breath', which, as I'm sure all of you know, is 'pneuma' in Greek. And what is the 'Holy Spirit"/"Holy Ghost" in Greek? Pneuma Hagios (I think). Of course, I don't know the etymology of 'ghost', so it could be just as valid.
In the end, it comes down to me liking 'spirit' better than 'ghost'. And yes, I know that's a really bad justification.
And I agree, AN, that was very priceless.