Hardware + Service
There is something to be said about the Hardware + Service + OSS combination. Often in a corperate environment especially, they are looking for solutions that won't disrupt the rest of their operation. A box that drops in, pre-loaded, configured, and ready to plug in is a good answer to that. It is also much simpler for them than to have an existing (and probably overworked) admin take on yet another system he/she has never seen before.
This can be especially important today when one vendor's hardware is about the same as another's. Something has to differenciate your system from everyone else's.