I actually bought a Samson C01U last night, so my experience with it can be expressed in hours.
So far, it sounds awesome. I was using a cheapie "PC" mic plugged into a Griffin iMic, and it was noisy and tinny. My test recordings with the Samson, made with WireTapPro on my iBook, turned out very nicely.
The one thing I would recommend to anyone who gets one these is to download the applet from Samson's web site. The volume level of the mic was a little low without it, but with the applet it sounds incredible.
My other recommendation is to get the spider mount for it. Since it's a condenser mic, it's susceptible to rumble and other environmentals. The mount keeps the sound clean.
A related question for the group-- does anyone know if you can connect two of these to a Mac, and if so, will GarageBand or any other apps recognize two USB devices? (My assumption is "yes.")