I very much enjoyed the Salkantay trek. I do not have too much hiking experience, but the guides and staff that are with you during the journey were very efficient, helpful, and knowledgeable.
I never felt "lost" during the journey or unsafe. The thought of doing a 4 day trek seemed too daunting at first, but if you are in reasonable health (I'm 28) and give yourself adequate time to acclimate to altitude (something like 3-5 days) you will complete it. The sleeping accommodations were overall quite comfortable and food was delicious every day.
I would recommend this hike to my friends.