I don't have a mac atm .. but do people still use iChat or was that replaced with Facetime which is available through the Mac Store for .99 Cents if I'm not mistaken.
I personally like iChat more as its universal and I can chat without voice or video if needed. Also, ichat supports more people VCing at once. Ichat also allows more clients such as AIM, Google talk and Yahoo, while FaceTime is centric to Apple users who currently have wifi. FaceTime is going to be the norm for now for sure, and hopefully they'll integrate ichat and FaceTime into one app making my life much easier. FaceTime and iChat both do NOT work with Skype (or msn for that matter). But to sum up, FaceTime and ichat have slightly different targets (also can you use photo booth effects in FT?)