When you choose an OS for your laptop, many things affect your decision: application support, availability of drivers, ease of use, and so on.
But if you were developing a storage appliance, what would you want from the operating system that runs inside it?
The first thing you notice is all the things you don't care about: graphics cards, educational software, photoshop... none of it matters. What's left, then? What do you really need from a storage OS? And why isn't Linux the answer? Well, let's think about that.
You need something rock-solid, so it doesn't break or corrupt data.
You need something that scales, so you can take advantage of all those cores the microprocessor folks will be giving you.
You need really good tools for performance analysis, so you can figure out how to make your application scale as well as the OS does.
You need extensive hardware diagnostic support, so that when parts of the box fail or are about to fail, you can take appropriate action.
You need reliable crash dumps and first-rate debugging tools so you can perform first-fault diagnosis when something goes wrong.
And you need a community of equally serious developers who can help you out.
OpenSolaris gives you all of these: a robust kernel that scales to thousands of threads and spindles; DTrace, the best performance analysis tool on the planet; FMA (Fault Management Architecture) to monitor the hardware and predict and manage failures; mdb to analyze software problems; and of course the OpenSolaris community, a large, vibrant, professional, high signal-to-noise environment.
The other operating systems one might consider are so far behind on so many of these metrics, it just seems like a no-brainer.
Let's put it this way: if I ever leave Sun to do a storage startup, I'll have a lot of things to think about. Choosing the OS won't be one of them. OpenSolaris is the ideal storage development platform.