As far as benchmarks go, a G5 Quad is considerably faster than a 2.2GHz Core2Duo. Granted (as people above have said), if you need to run the "latest and greatest," you might not want to dive into the PowerPC world. As for me, I'm perfectly happy with my day to day use (iTunes, internet browsing, writing papers, and YouTube). The G5 PowerMacs are about the only PowerPC computers that can handle high definition Flash video without dropping frames. I used to have a 1.25GHz iMac G4 17" and it really struggled with any video above 360p.
EDIT: As far as video editing goes, I think it'll work well for you...but it's certainly not going to be as fast as a current generation i7 Macbook Pro or any Mac Pro but it's a great computer for the money and offers a lot of expandability. Just keep in mind you won't be able to run the latest Final Cut or iMovie on it.