The old Serial library has some problems when used in .Net CF 2.0 applications. This is a beta release of a new library that is based on .Net CF 2.0 and therefore should work properly. See this instructions for targeting .Net CF 2.0: www.basic4ppc.com/netcf2.html These instructions are not required for WM6 devices. The library functionality is the same as the old library. It supports both the desktop and the device. Currently, it doesn't support IR communication. Please use it and post any question or feedback about it.