The natural beauty of the Salkantay trek is without doubt the most beautiful I have ever seen.
This is coupled with an amazing staff that make the trip unique and personal. If you have any optional parts of the trek, no matter how exhausting, do it. The side trails lead to views and ruins few will ever get the chance to see.
Of course this shall leave you out of breath every time, but the exhaustion only contributes to a sense of accomplishment rarely felt. My only complaint is that the trek makes the rest of my life look dull and boring, curse you Jorge, Raul, and Alejandro!.