Impression is free with any Autodesk Subscription, you just have to download it from the subscription center.
I also work for a civil engineer, but most of our work is small developments, and so far we've only used Impression for presentation of two projects. One was a motel site primarily to show the city council something that they would grasp easier than a black and white line drawing. The other was a parking lot for another city so that they could grasp the landscaping and paving improvements better.
It certainly works to wow the laymen who don't completely grasp the line drawings that most engineers provide them 😉
I'd say it's worth the time to learn (which it is pretty easy to pick up, its fairly simple), and it can reload the dwg file used to originally create the drawing, so that major design changes can be reflected in the presentation fairly easily.