MSN Messenger - Good voice quality and video quality. Decent text messaging [for PMs... I never used the MSN rooms]. Downside is that w/o WLM 8 you can't do offline messaging.
Yahoo! - Good voice quality in rooms. With v7 I hate the new PM voicing system. Video quality is so-so. Text chatting in rooms is so-so but in PMs it's junk since I can't seem to receive or send any PMs lately from the people I want. The program as a whole is a pile of dung, IMO. It's one big bug riddled client.
Eyeball Chat - Good voice and video. You can do a lot of tweaking with how it uses bandwidth. Yucky text chatting. Unfortunately this free client hasn't been updated in a long time but it still works and it's great if you have problems with firewalls, etc.
Camfrog - Great video and voice quality. Good text chatting. Nice solid program that is basically Yahoo on steroids and actually works. Downside is... no offline messaging.
ICQ - I haven't used it in a long long time. This had probably the best file transfer of any chat client.
mIRC - The old standby. Text-only but it works and does the job. Of course you need a decent IRC server to join but if you can't find one then you shouldn't be using a computer.
NOTE: My opinions were purely based on person-to-person chats and no using a "room" within the client if the client supported rooms.
Ep, glad to see you come back and tidy up...did want to ask a one day favor, I want to enhance my resume , was hoping you could make me administrator for a day, if so, take me right off since I won't be here to do anything, and don't know the slightest about the board, but it would be nice putting "served administrator osnn", if can do, THANKS