I confirm the problems with openJDK 8 (at least with current version 8u66-b17-1), I'm unable to even run the netbeans installer, while using Oracle JDK it works fine.
If I install netbeans with Oracle JDK and then run it with OpenJDK 8 the experience is VERY bad, with very long pauses here and there, making it almost unusable.
I confirm the problems with openJDK 8 (at least with current version 8u66-b17-1), I'm unable to even run the netbeans installer, while using Oracle JDK it works fine.
If I install netbeans with Oracle JDK and then run it with OpenJDK 8 the experience is VERY bad, with very long pauses here and there, making it almost unusable.
It used to work fine in Ubuntu 15.04