No, not really. The video conferencing offered by most ISPs (though not all) is of a MUCH higher bandwidth. iChat is cute and all, but try adding more than 4 or 5 people to it and see how well it works.

Not to mention that true video conferencing usually involves a dedicated camera and TV set, which can capture an entire conference room, with separate audio/video sources, etc. in the software.
The Graphic Mac - Tips, reviews & more on all things OSX & graphic design.