Is 做事 just Taiwanese, or does it have a different flavour than 工作？ My first book (1987 Edition from Taiwan) taught 


  你在那裡做事？ 我在中國大學教書。
  (Throughout the book the 口radical in 哪 was omitted.)


Ever since, I have been looking out for 做事 in my textbooks from the PRC, but haven't once noticed it. Is it just uncommon in the PRC, or does it convey a humble tone, as - I am told - 教書 does?
I think you are right - "做事" is probably only used in some areas of China, especially some southern areas where ancient Chinese has an influence, and not as commonly as "工作" in this sense. I would say it is more colloquial than the latter, too - for example, I think an interviewer will more likely to ask "你之前在哪里工作？" than "你之前在哪里做事？"