I understand the formal word for cellphone/mobile phone is the same in both countries, i.e. xing2dong4dian4hua4. Not sure if shou3ji1 is used in China now, but it’s highly possible. Ditto ba4gua4 (gossip). My (mainland) Chinese teacher turned his nose up at that one but admitted that it’s catching on. He still prefers a more starchy word, yao1yan2.
In China a first or second tone at the end of a word is commonly dropped, e.g xian1sheng1 (sir), xiu1xi2 (rest), xing1qi2 all lose their strong last tone in China.
In terms of different vocabulary, it seems more recently created vocabulary, e.g. bike, CD is likely to be different on either side of the strait.
More likely to trip you up listening-wise is different grammatical preferences. Also I can’t help thinking when I read newspapers from mainland china that they use much more anglicised language, though I’m not learned enough to be completely sure about that. Overall mainland Chinese sounds a bit more blunt. You’re unlikely to hear people say ‘bu!’ for ‘no’ in Taiwan, ‘bu shi’ or ‘bu hui’ are preferred.