I'm working with a company that is putting in a new architecture for sering a web application. They've gone with a SAN for the data storage, allowing multiple servers to hit it. 15K drives, I'm not sure how many or what brand they ended up with, but I'll look into it further.
I will say while I find the idea of jamming SSDs in there to be fun, these guys could barely afford what they bought already, so high capacity SSDs were out
It would be pretty fun to test one against another though to see what the real world results would be, not so much at the sever, but if the user notices it through the browser.