According to Wikipedia entry on Taiwanese Mandarin:
The official Guoyu is almost identical to the official language of the People's Republic of China, called Pǔtōnghuà, with the exception of their writing systems. However, Mandarin as spoken informally in Taiwan has some notable differences in vocabulary, grammar and pronunciation with Standard Mandarin
I wonder whether Standard Mandarin can be understood by Taiwanese if simplified characters are mapped to traditional ones (in written context). There still seem to be differences in vocabulary and grammar but how are that different?