I was at a conference with a Sun evangelist banging on about this stuff. I was pretty skeptical. One of our Hadoop grid sysadmins used to work at Sun. He was raving about things like D-Trace and a bunch of features of Solaris that other *nix don't have.
I guess I'm not 100% sold on Open Solaris but they do have some pretty badass stuff in there.
Its nice that they release the fruit of their labours in OpenSolaris.
I've rolled my own hybrid storage and played with it in ZFS using a RAM disk and flash storage and it really does work - it can make a RAID of slow SATA disks look like a bigger RAID of fast 15krpm disks, provided all your workload fits in the various ramdisk/flash caches.
Sun went out of their way to make an amazing storage product. Interestingly, they started with perl, then rewrote everything in JavaScript/C instead[1].
