STM32F4 - CMSIS & Board Specific Libraries
I strongly recommend the libraries.  A big advantage of cortex M is to be able to easily move your code to other members of the same family (i.e. STMF0 to STMF4), or even to different manufacturers, and you lose this advantage if you don't use the libraries.

BTW, many vendor specific libraries are CMSIS compliant.

I've avoided families that don't supply CMSIS compliant libraries.  Also, I've not tried STM Cube for much the same reasons.