For the adventurous, interesting times ahead since you're able to try out the NetBeans IDE 9 development build on top of JDK 9 EA, in my case, Build 162.
When you configure that in your 'etc/netbeans.conf' file, the first thing you see on start up is this error, which appears to be related to the Darcula plugin that I'm using. Of course, since it's awesome despite this aspect for the moment, I'm using the Darcula plugin, which you can download and install from here, i.e., simply use the latest release of the plugin for 8.2, works fine in 9 development builds, except for this error.
After seeing the above, simply click Cancel, and, so far, despite the above, things are pretty good!
There are two big advantages to running the NetBeans IDE 9 Development Build on top of JDK 9.
The first is that the fonts are automatically a lot better, at least, on Windows and, at the very least, on my system (click to enlarge the below, where you see NetBeans IDE 9 Development Build on JDK 9 on the left versus on JDK 8 Update 121 on the right):
The second advantage is that you automatically have JShell integration (choose Tools | Open Java Platform Shell), as shown below. Excellent enhancement here is that, since the last time I used it, there's now a code fold for the text at the top of the JShell.
Until further notice, this is the environment I'll be using.