Sorry but that's bull
With the current SSD prices still being high compared to normal HDD's, a 120 GB SSD drive for your OS and most used programs is PERFECT
Load your most used data on a Seagate Momentus XT Hybrid 500 GB drive in the Optical Bay slot.
Of course if you can afford it, get a MacBook Pro 17 with 2 internal SSD drives, one for programs and OS and one for your data - but it gets pretty darn expensive, so for people on limited budget, a 120 GB fast SSD for OS and programs is a great idea !
Yup! I have a 120GB + optibay and I could even have used a 90GB and be fine. Also considering WoW and SC2 take up about 45GB themselves, the OS + apps are only using up about 25GB for me. So yeah, boots, app launching, all that is soooo freakin' fast. LOVE IT!