I'm flying out of Florence to Paris to go to New York. I'm not sure, but I hope it's not a nightmare.

I haven't read the other postings on this thread but I must say that Munich would get my vote. It is a newer airport, well laid out and beautiful inside. I am not familiar with Manchester or Brussels, though.

Paris gets my thumbs down. I do anything not to fly through there. CDG is badly set up and it takes a ton of time to get through. Zurich, London and Frankfurt are reasonable, but Munich is just so easy compared to them!
Cheers,
Jan