The Gimp is nowhere near PhotoShop, in any stretch of comparison. Sure, they do similar things. Portions of The Gimp even resemble PhotoShop very closely.
Whomever on G4 TV insinuated that it was even close to PhotoShop in any way, shape, or form has absolutely no idea of what they're talking about.
That's like saying that a VW Beetle is comparable to a Ferrari. Perhaps they're in the same solar system if you use them for going back and forth from work, but if you use the cars for what they're really intended, the VW hardly looks anything like a car when compared to a Ferrari.
Anyone who uses PhotoShop in it's intended, professional, productive environment would know this. Those who only know PhotoShop superficially may be tricked into thinking that The Gimp and PhotoShop are on basically the same level, but that is simply because they either have not learned PhotoShop in-depth, or have no idea of how much more powerful PhotoShop is.
Don't be fooled into thinking this way -- it's poisonous.
With that being said, I can attest to the fact that The Gimp is an extremely powerful, semi-easy to use, free image editing program.