qi si wo le ! not every word which contain 'si' is showing angry mood. 'si' here is express a deep level. like 'xiao si wo le(笑死我了)' means 'I nearly died laughing' . 'tian si le(甜死了)' means 'much too sweet ' and 'gao xing si le (高兴死了)' means 'be extremely happy',,, and so on...

I usually use it , when something pissed me off.. and I think it's ok if you use it..

it is ok ,i guess. because here you die ,not other people (joking ) just if you cant pronounce it correct , it can be a bit funny . O(∩_∩)O

I usually use it , when something pissed me off.. and I think it's ok if you use it..

It should be "qi si wo le". :) I think it equals to "it pissed me off" in English and it's ok to say that. Elise has answered for the reason.