So earlier today I complained that the HTC Artemis/Orbit/MDAIII has different features for different countries. Now that we see the T-Mobile MDAIII has been announced, here's the rundown on the differences:

O2 Germany's HTC Artemis: GPS with onboard navigation. no W-LAN
O2 UK's HTC Orbit: GPS with onbaord navigation, W-LAN included
T-Mobile Germany's MDA-III: GPS, but you have to use your data plan to get directions, no W-LAN

All of the above have a TI OMAP processor, MicroSD, and a 2 megapixel camera. Looks like the Brits get the best version, though.

Unlike O2 Germany and HTC, T-Mobile isn't giving an onboard navigation solution with the MDA compact III but is offering navigation via T-Mobile's own NaviGate offboard solution only.
This means that for every route calculation, the device connects via GPRS or EDGE with T-Mobile's NaviGate server to get the route calculated on the server, which transfer the route back to the device after calculation.
NaviGate is able to calculate routes for 18 European countries, a single route calculation for German costs 99 Cent (including GPRS/EDGE traffic charges).

Read: the::unwired - ANNOUNCED: T-Mobile Germany announced the MDA compact III aka HTC Artemis