The Garmin iQue 3600 runs Palm OS 5.2.1R3 (to date). It has all of the productivity features that are associated with the PalmOne platform. You can also run any third party apps designed for the Palm: PalmReader, Documents to Go, etc. It is a very graceful melding of a Palm powered device with the full featured functionality of a GPS navigation unit. Granted, a few accessories are crucial to a satisfactory experience: 512 MB minimum SD card (I use a 1GB), the car adapter kit and an FM modulator for in car navigation.
With that setup, it rivals the NAv system in my Honda Odysee EXL-NAV, with the added benefit of being able toa ake it with me when I travel.
I use the iQue 3600 daily and to its full functionality and highly recommend it. If you buy one, be sure to make sure it has the latest OS updates. Some of the older versions of the OS were flawed, but all the remaining bugs have been worked out in the latest release.