GPS ID stands for GPS Intermediate Driver
What this is (added in Windows Mobile 5.0) is to use Windows to ask information about the GPS device, not accessing the GPS device itself. Utilizing the COMM port will lock the COMM port for access. This was a problem so Microsoft made the driver for developers to use. Google Maps uses this driver while in TomTom you have to manually select the COMM port.
Having Windows to read the COMM port keeps it open for other applications to use. It's also faster since it's working as a device driver to the GPS hardware. I'm not sure if HTC updates the driver but the driver takes care of calculating speed, altitude, latitude, longitude, etc as well as parsing the NMEA information.
I've seen a lot of different tools all opening the COMM port directly and as a developer, you shouldn't be doing this, not unless you're using PPC2003. I believe (and this could be just wishful thinking) that GPSID is faster at getting a fix than COMM based. I could be wrong, but that's where you guys can help.
So here's a simple GPSID based GPS Tool. Include the Microsoft written DLL (Microsoft.WindowsMobile.Samples.Location.dll) with the executable.
Maybe I can make a simple application to stay keep the GPS open in the background and if you run it again, a message box appears saying "GPS is closed" or something (like S2U2) does.
(Link soon---bug testing)