@elmer: Not "all?". When finding a USB/Serial adapter it is important to see what chipset it uses and if it handles both hardware and software handshaking. Once you find one that meets those criteria then you have found a rock solid adapter. USBG-232 has been rock solid for years. http://www.usbgear.com/usbg-232.html
The support and development folks have been at odds for several years now over this. Support still encourages users to install the converter instead of using USB/(Activesync/WMDM) because it is an instant usable connection and simplifies user life.