Small energy efficiency boosts are great, and I definitely prefer anything environmentally friendly (it is really the heavy metals in the CCFL and not the energy efficiency that is accelerating the change), but... that business case is just silly. Even if you keep the notebook long past its generally-accepted usable life, I find it quite unlikely that you'll save $100 in energy costs before it dies.
At a power savings of about 1 watt (generous), and the average 2007 US power costs (10.6 cents / kWh), $100 = 943 kWh = 943,000 Wh. So, if you run your Macbook continuously, with the screen constantly on, for 107 years, you'll save your $100.
Of course, $100 is also an absurd cost estimate for an LED display assembly...