Why run a Custom Operating System???

I currently run COS 5 and have tuned everything pretty acurately but I find myself lately wandering why I dont want STFT,LTFT,MAF measurements, and why I even run COS 5????? I understand it helps greatly when running boost but I am naturally asperated.....
So I beg to ask the question.....
WHY WOULD I WANT TO RUN CUSTOM OPERATINGSYSTEMS IF IM NOT BOOSTED???
What are the advantages to a GM OP?
Thanks in advance to all!

mafless lets you retain both spark maps
fully commanded fueling is also a good plus
plus iat ve correction table, oh and tps ve

Thanks ringram!!! I remember getting help from you before. I did some searching throught the COS discussions and I believe I decided to just sell my MAF anyway. Thanks again