*laugh* Are people still waiting for the corpse of OpenSolaris to wake up from the dead and start doing something again? I like ZFS and all, but using something that is so marginalized at this point seems like a "Bad Idea"™. I'm not referring to bitcoind specifically. I just meant as far as operating systems go.
I'd also like to add
OpenBSD to your list. Hell, I'm not even sure bitcoind works on OpenBSD. From what little searching I just did, it seems like it doesn't yet. That seems like an oversight since it's always billed as one of the most secure operating systems in existence, out of the box anyway. Having said that, encfs under FUSE in any Linux still seems like the best way to go for now until the wallet natively supports encrypted private keys. And even then, it would probably be a good thing to keep it on some kind of encrypted file system.