This year we've been going to Santiago a lot during different times of the day, even at night, and I've been surprised. I honestly thought we would have to be looking over our shoulders. For instance, I thought that monument area would be dark and dangerous, but In the evening there are lots of people relaxing, walking or doing aerobics, families and couples hanging out, taking pictures. Restaurants are also active with lots of people. There are lots of vendors trying to sell you stuff, and people begging, but that's pretty much it.
Having said that, I do agree that crime has increased and that you should always be aware of your surroundings.