I hiked it a few years ago and I had a great time. The hike I did was a four day hike. There are porters who will carry most of your gear if you pay extra. I didn't think the hike was very hard, but I am in good shape and live at 10,000 feet. One of the passes you hike over is pretty high, but chewing cocoa leaves helps out.
I hiked it in late Novermber so it was the middle of summer down there and pretty warm during the days, but it cooled down at night. There is a rainy season down there, but I forget when it is.
I was in some pretty sketchy areas and never had anything stolen from me. Some people I talked with had things stolen from them while traveling on busses. Cell phones, ipods, sunglasses taken from their packs. I talked to one person in the US who told me they were robbed at knifepoint while in Lima. I felt safe while I was down there.