With this DLC, you'll get new leisure night activities, beach tourism, and more forms of transportation -- like taxis and bicycles. There will also be new prisons, plus new city policies on education, prison sentences, and taxation.
The main feature advertised in this DLC preview -- the day and night cycle -- was added to Cities: Skylines for free. This expansion isn't necessary if one simply wants to have that cycle. Additionally, there aren't enough tourists to utilize the great features it offers.
You want to optimize the free content released in the patch. With the addition of new lanes for buses and riders comes traffic lessons. Crime is reduced once a prison is placed and its corresponding policies enacted. Your city will run much more smoothly with this expansion installed.