Agree with all advises above but in order to get the most out of the M (Manual Mode) you need to be able to control your shifts, when to up-shift and when to downshift, just like a manual transmission.
The Manual Mode allows you to push the car further and control the car's response depending on the RPM.
2 important things you wanna do to have better control and reduce shift-timing:
New Paddle Shifters + Transmission Tune
Pierre777 and 100s of other members are using our
Paddle Shifter extensions and were very satisfied with the result.
They allow you to control your shifts much easier, no need to be looking for those hidden buttons especially when steering!
The other important step is to get a TCM (Transmission Control Module) Tune that will reduce the shift time and firmness the way you like it.
Have fun !