Windows 10
Unity 2018.2.0b7
Visual Studio 2017

Steps to repro:
1) Open an existing project (that has scripts) in 2018.2.0b7 (on a windows 10 machine)
2) Create a new script and open it in Visual Studio
3) Observe that Intellisense stops working
4) Note that Intellisense is fine when opening existing scripts

Intellisense only starts working after restarting Unity and Visual Studio

Also reported here: https://developercommunity.visualstudio.com/content/problem/130597/unity-intellisense-not-working-after-creating-new-1.html