I just finished my first coast-to-coast video chat with my grandmother, and I couldn't be happier. Apple has a major winner with the iChat/iSight combination.
It wasn't perfect - there was some video compression artifacting and the sound occasionally dropped out, but it was good, which is better than the alternatives.
We had a full 15fps during the entire call, and the sound was remarkably clear. My parents were with my grandmother, so there were actually four people in the conversation, and it was never confusing.
If you want to keep in touch with friends/family/enemies/whatever, then I can't recommend iChat/iSight enough. The only problem is that you must have Macintoshes on both ends for it to work. If you can deal with that, though, then there's nothing better.