It's not that their not very Mac friendly, it's just that there are many more PC's in the world than Macs and ISPQ devotes more time to upgrading the PC versions first. ISPQ does work well, better than any other I've tried except iChat, and I've tried most. The big advantage of iChatAV is that you're not using someone's server to communicate, it's direct, and the sound is Duplex, like a phone, much better quality.
Like I said, it's "Rummored" that a Windows version of iChatAV will be avilable by the end of the year, no guarantees.
I talk regularly to a couple people using ISPQ, one in the UK and one in Australia with no problems, they both have PC's.