Here is a little life sign from OMV. The newest video shows you the installer live in action. After a short installation phase OMV can be used out-of-the-box.
Note, OMV uses the whole harddisk selected during the installation for the system OS. So if you’ll use a 1 TB volume for that you’ll waste 999 GiB of this disk for nothing. That’s fact, nothing will be changed in that way. No stupid OS/data partition solution as in FreeNAS will be supported, instead use a small HDD (maybe an older one) or better a SSD/DOM/whatever. Currently the OS requires about ~250MB in summary, but this may increase in future.