I got a message on Facebook.com from one of my viewer who is going to study in Shanghai, China for a year. He asked me a few questions I believe many Mandarin learners have in mind as well when beginning this stage. So I think it might be helpful to some people to share them on here.

Q. “Is Taiwan Chinese the same as China's Chinese?”

Spoken Mandarin in China is called Putonghua(普通話) and Taiwan Mandarin, Guoyu (國語) are mutually intelligible in general. The most different part, I would say, is the writing system. China uses simplified Mandarin (e.g. shi2 me5什么); whereas Taiwan uses traditional characters (e.g. shi2 me5什麼) 

However, there are differences in other linguistic properties, such as Pronunciation (Phonology) and Lexicon (Vocabulary):

Q. “Are tones really important?”

Tones are fairly important as they decide whether what you say can easily be understood by Mandarin native speakers or not. In Mandarin, a word can appear to be in the same tones and the same Pinying, but different in written characters. Therefore, if it's pronounced with the wrong tones especially when spoken, it could be interpreted as a completely different meaning. 

An example of a mistake many foreigners in Taiwan make when speaking Mandarin is: 

shui4 jiao4(睡覺) - sleep 
shui3 jiao3(水餃) - boiled dumplings 

One would say "Wo3 yao4 shui4 jiao4 - I want to sleep" when s/he actually meant "Wo3 yao4 shui3 jiao3 - I want dumplings" Listeners could probably still understand what the speaker means from the context but it could be confusing sometimes. 

I hope it helps! 

Happy learning! :)