My experience as a world traveler has been severely limited: one week each in England and Ireland in August of '04.

Most of our stay in the UK was at my brother's home in East Anglia, but our one overnight in London, plus the week traveling across Ireland, involved overnight stays in B&B-type establishments where every proprietor was anxious to demonstrate to us "Yanks" that they knew how to make good coffee.

And, indeed, every morning's brew proved to be more than passable (and some were downright excellent). I would have been glad to "do as the Romans" and stick with tea as a morning wakeup, but took the coffee to be polite. Never regretted it; had to wait til afternoon to experience nice cups of tea at, well, teatime...

I can't name a single specific "worst" cup of coffee. I generally dislike instant, but my real pet peeve is non-dairy creamer. I'll use it anyway when unavoidable, finding it just barely preferable to black, but will go to lengths (including paying extra for a glass of milk) to include a shot of real dairy product.

My normal preference is cream-no-sugar, but when faced with the prospect of imbibing nasty chalky powder-cream, I will sometimes resort to sugar to kill the aftertaste.