One point I'd like to make that might surprise some westerners is that Chinese think it is extremely rude to not take off your shoes when walking into someone's home (and would never do that themselves - so you always see indoor sandals or the like at the entrance to any typical Chinese home).
Yet many westerners will come into a Chinese home and just "walk in with their shoes on".
So things that people think are disgusting or inappropriate do vary from country and country.
I think this all depends on how respectful someone is. I live in the UK and its not customary or expected but
most people (including me) at least offer or ask if they should take their shoes off. I'd rather keep them on if they're not dirty personally but I always ask.
That is interesting as most Australians would not (so would you consider most Australians to be rude?).