Unfortunately your experience as a graduate at Mars will very much depend on the placements you are given and the manager appointed to you. This can feel very random. Many graduates have left Mars mid way through the scheme or after, due to a lack of support from those who are supposed to be providing it.
The MMDP is high profile and challenging, but very little is done to retain good talent at the end of the programme which is why so many talented employees leave to pursue careers in companies where they will be recognised and rewarded fairly.
Mars is slow and frustrating at times - it is not the place for those with an entrepreneurial spirit.