I did the update a few months ago. The update brings the map data current as of Q1 2018. Previously it was at Q1 2015. It's an approximately 14.5GB download.
For $110 it was worth it for me. I also use a phone along with google maps and waze but a lot of my work is in areas with no mobile/internet coverage and the built in nav system has got me out of a few jams, especially at night.
This is a good explanation that brings a balanced opinion on spending the $$ or not. I am a Waze fan and 99% of the time am within cell phone coverage...so for me, no update needed.