I've used iSpQ, ICUII, iVisit, CuSeeMe, iChat AV.. you name it. I remember when it was between ICUII and iSpQ, and it looked like iSpQ was a cheap rip-off of ICUII.
Then.. ICUII dropped Mac support. That was some 3-4 years ago, and they haven't been back since. In that time, iSpQ has really surpassed anything ICUII could've ever dreamed of, and I'm happy to see they've now got the Mac version on full par with the Windows version.
iSpQ 6.0 really is a totally different ballgame from past versions. I've been beta testing this for the last 4-5 months now, and I'm glad they've finally got all the bugs worked out. Now they support full video and audio chat with up to 4 different people at a time, Quick Messages (ispq's version of IM'ing people) with Audio, Video, and full-color text/font styling support, directory chat, directory listings, and apparently (though I've not had a chance to test it) their "MyPlace" feature is working, too.
I just wish this program would get adopted by more people, cause it really is a great app/community. But, the price tag tends to scare people away, I guess.