They are not very usable not very good. They fail a lot of the time and/or are extremely buggy.
I've had phone calls with Greg Kroah-Hartman, extended private e-mails and some mailing list threads.
In fact I have one sitting here. "certified" to work with OSX and Windows Vista and Windows XP.
I also have a USB to PCMCIA adapter. Works better than the USB to ISA Adapter and lets just say... just better.