It depend on the cases. Basically, Using them is not rude and I think over sea people can get more understand than our using. but, I suppose there are some cases what are actually difficult to use them by the situation of each restaurants. for examples, traditional Japanese restaurants have severe rule to eat. I have never seen the people to use them at sushi restaurants (at least in my experience) and formal tempura restaurants. soba noodle and ramen and these restaurants's system are not used to eat slowly. of course, some supportive and kindly restaurants of them can understand for using . but , these are not all and these kindness might be change by cases.