a winmodem seems to me to be half a modem, with the other half of the modem being emulated by a program (closed source, windows only). My sister got one of these, as she was owed a modem off an ex boyfriend who nicked her old modem, and he gave her a "software modem". She says it was shite even in windows, and she promptly bought a similar modem from the same company, but made sure it was a "hardware modem", so it runs independently of the OS, whatever it is, and only needs drivers. Apparently, the manufacturers' drivers don't really provide optimum performance in windows, whereas Linux autodetected it on install.
The main problem here is that a casual user, trying out a free UNIX for the first time, might assume that the winmodem not working problem is a unix problem rather than the fact that they have just been stiffed by somebody that wanted to seel them only half a modem...