I ordered a Samson CO1U USB "podcasting" microphone to use for my upcoming podcasting workshop. Brian has one, and it's a beauty. Nice and heavy, and seems to have really nice and rich audio quality. Better than my little USB headset, Powerbook built-in mic, or iSight camera offer, anyway. It was cheap, too - under $80.
After I opened the package, I plugged the USB cord into my G5. It was recognized right off the bat, and iChat and Garageband were able to use it with no additional installation. Then, I went ahead and installed the Samson "applet" to get additional tweakery and bitfiddlery.
Don't install the applet. It also drops a kernel extension into your system, and requires a reboot. Sure, it gives you a cool-looking levels controller, but it also makes the microphone invisible to audio apps. I'd rather have a stock mic that works, thanks.
So, I uninstalled the .kext and rebooted to clear it out. The mic is visible again. But not to Audacity, for some reason. I'll debug that tomorrow.
First reaction is: the mic (when it is recognized) sounds really nice. Is the flakeyness worth it? I'll know more in a couple of days of playing...