IF you can use iChat successfully with an AIM user, it works great. Of course, your video (coming from you) will **ALWAYS** look and sound better than theirs (PC users have such CRAP webcams!!), but it will work fine if it works at all.
I also have had more consistent results with Skype, which works on both platforms but can cost money in certain situations, so try iChat first.
i greatly appreciate all the responses! reading between the lines it seems like if you can get the iChat/aim thing working you're probably best off (thanks for the link on configuring aim Vexel!). maybe i should have stated at the outset, but i'm asking this because my daughter has regular tutoring for a reading disability and i'm looking for a way for her to check in with her instructor while we're away for a few weeks over the summer (we're mac people and her tutor has a win based system). i'm assuming that smooth video will the most important thing (she'll have a lesson book with her and won't have to read things through the chat window) since she'll need to feel like she's really talking to her teacher. i'm concerned that skype will not be smooth (my experience with it a few years ago wasn't positive, it wasn't even close to iChat) but i'm sure it's improved since then. i do still wonder what gtalk is like though. anyone compared it or skype directly to iChat? thanks again, what a great community!