It's not useful, but it is interesting. Some of the UI around the Mac/UNIX interaction is very different than they later went with with OS X: some of it better (Commando is one of the big missed opportunities), some of it worse (HFS volumes vs. UNIX volumes is a bit ... peculiar).
From the UNIX side of things, it's just an old UNIX, and there's not a huge amount special about it.
From the Mac side of things, I do find the ability for each user to have their own System Folder to be nearly useful, my own installation has a number of accounts with different sets of extensions, for example. But that's not very useful. And the potential of the hybrid toolbox is kind of cool. But, again, never really materialised beyond a few applications.
But there's no real reason to run it beyond a modern UNIX, and unless you're ready to treat it as a security nightmare waiting to happen, it's perhaps best avoided as anything other than a desktop OS.