as far as I know ichatAV video Conferencing on works MAC to MAC although you can send Im's to AIM on other platforms.
The isight is also quite costly if you don't have a firewire cam.
However, I changed over to a mac around last year and to be honest have't looked back since.
I am currently in the process of selling my remaining pc's and converting my wife and daughter to Mac also.
Good luck with your purchase