G Fong is charismatic and pursuasive in a BS kind of way, and Americans love him. His products work, but often not as well or as efficiently as cheaper (or free) alternatives. Plus they are expensive and bulky.
Efficiency is crucial with this kind of stuff as the moment you start bouncing flash around the light just gets gobbled up in huge lumps, and you haven't got much of it to start with, even with a big hot-shoe gun.
I'm a big fan of Lumiquest, because their stuff works well, are as efficient as these things can be, and they fold flat. Their video demos are also honest and to the point, and brief - if you're new to this stuff, I would watch them all. I particularly their Quik Bounce, because it is so versatile and easy.
I also carry a Stofen-type diffuser cap (the press tog's favourite) which does pretty much what the Fong does, but only costs three quid on Amazon/ebay and slips in your pocket. Buit I only ever seem to use the LQ Quick Bounce
Another one that can turn its hand to a variety of situations is the Demb Flip-it Classic
http://www.dembflashproducts.com/flipit/models/ It's just a glorified bounce card similar to the hi-lite panel built it to most guns (same idea as this
www.abetterbouncecard.com ) but it's neat, effective, and handy.
PS always remember that the result you get with any diffuser that spreads the light around is entirely dependent on the nature of the surroundings to do anything at all. You need a ceiling or walls, preferably white and close by.