I just purchased a Amix X30 pocket pc. I want to purchase a GPS accessory with it, but I'm not really sure if it will work well for hiking and backpacking needs, GPS wise.
I would suggest buying a stand alone GPS unit instead of the attachment for the Axim. Mainly because they are not as fragile as the PDA and offer a bit of water protection in case you want to use the device in the rain.
Also:
* complexity--a single sealed unit will be much more reliable under field conditions than several units connected together.
* time--a dedicated GPS will most likely require less of your time to operate. Your partners are not likely to want to wait around while you play with your electronic toys.