I'm pretty sure you can reduce the entropy of the output by saturating the processor or memory. If the various accesses are being spread out more because other processes are executing then you're going to have substantially less entropy. Sounds like bait for a DoS attack... hit the server really hard and all of a sudden the RNG is producing bad random numbers.

I doubt it's more efficient than something like Mersenne Twister. Generating entropy this way is pretty damn expensive in terms of processor cycles.