When it comes to random seeding, I've always thought the best option would be to use every source available, and hope that at least one is high quality. If we combine:

* RDRAND * Seed from previous boot * Jitter * Result of every sensor (for example temperature) attached to the machine * Seed from hypervisor (if we are in a VM) * Time & Date * Any information about the physical computer we are on (attached hardware)