Great (big) city.
Santiago isn't really like the rest of Latin America; it kind of sits more in line with major cities in Italy or Spain - very safe, very developed, very clean, but watch your things in crowds, don't use your phone on the metro, etc.
It's a lovely city you can spend a long time walking in - most of the museums are free, the architecture is lovely. The mountains make great day trips, and the fish/seafood is fresh. Winter's smog is pretty annoying, and prices can be pretty steep.
Insider Tip:Go on a couple day trips to the mountains - there's lots of great hiking. Take advantage of the free walking tours (10 am and 3pm at the Plaza de Armas) early so you can get some local advice. Eat in the central market one day.