Nothing particularly special. Their proprietary technology gives you some minor improvements in performance, reliability, and power efficiency relative to what

Nothing particularly special. Their proprietary technology gives you some minor improvements in performance, reliability, and power efficiency relative to what you could assemble into a rack yourself. But more importantly for large enterprise customers they give you a single throat to choke: if something doesn't work then you can call them up to fix it with some assurance that it will get handled quickly. They won't point fingers at another vendor.