I have managed to configure a wireles PCI card on CentOS 5.3 and it seems to work fine.
It is a off brand (Hercules) with a Ralink RT61 chipset. I installed the most current driver (RT2501PCI/mPCI/CB(RT61:RT2561/RT2561S/RT2661) from the rt2x00 Open Source Project. I now have a question that might be very simple for one or more of you to answer. When I issue the command "shutdown -h now", the machine starts to come down and brings down eth0 cleanly, but when it attempts to bring down wlan0, the machine hangs and never brings down the interface OR powers off the box. The only way to complete the power off is to "hard" power off the machine. Any ideas? Thanks for all the help!

No idea. Nothing in syslog about it? Could try to do the reverse of how you would bring up your wireless manually and then shutdown. If that works you could add it to the shutdown part of your network initscript.