They are very nice and the GUI looks very good visually.
The tabbar in the middle works somewhat strange though. Sometimes tab appear somewhere in between and it seems it still could use some work. The level of functionality is good, but it's not always clear where to go.
The biggest problem i think is that FreeNAS is stripped down. This means lower RAM usage but does make it more difficult to add stuff manually. I plan on making ZFSguru based on normal FreeBSD, and as such people can choose which version of FreeBSD to run using separate system image releases. This allows me to create experimental images with new functionality ready for testing or preview.
FreeNAS always lagged behind considerably with FreeBSD releases. But i think they should have that under control now, being rewritten and maintained by new developers.
Seeing these screenshots my interface looks old fashioned and dull; i should fix that in 0.1.8 final when themes would become available to radically change the visual appearance of all pages. That should make it more pretty.