They basically saved Java when they bought it, tons of great features and quick updates nowadays. There was almost zero innovation for about a decade while it was with Sun.
Their treatment of OpenSolaris is unforgivable in my opinion. We can now run ZFS on mainstream Linux as of a year or two ago, but it's too little, too late.
ZFS is mostly developed by the OpenZFS community, not Oracle. OpenZFS is creating all the new developments, including ZFS on Linux, while Oracle is over in the corner with their little fork, pretending it doesn't exist.
To put it more succinctly: Oracle ZFS is OpenOffice. OpenZFS is LibreOffice.
Yes, what I mean is Oracle could have relicensed it so that the Linux ZFS port could actually be in the kernel source tree.
They also crippled Java on Android by suing Google.