Garf.org bullet proof reef plenum or not to plenum??????

[ati70cutlass]

so ive been scratching my head at building my wifes 40b so that she will have no problems keeping lps/softies with minimal effort. i went back to the garf.org website and checked out the bullet proof reef. the only thing im curious about is the use of a plenumn style system under the sand bed. ive never really built this system before and am wondering does it have more benifits rather than cons. any ideas?

http://www.garf.org/bulletproofreef/BulletProof.asp

please list the pros/cons to this type of system. they say thier oldest bulletproof reef is over 12 years old with no crashes ever.