I can only speak from my experience. I just think paying $100 for one is a little much when a non-Winmodem can be bought for less. One brand that I had good luck with was Newcom. I've seen them as low as $59.
I spoke with the technician from my ISP and he said that they found that Winmodems (Usr) are unreliable. He recommended the ISA Usr Sportster FaxModem that he was selling at $129. He said they are more solid.
Myself, I've spent $100 on a Winmodem and wont buy another Usr because mine has a 5 year limited warranty and they have not offered to fix it, and I've called twice to tech support with the same problem.