I recently went for the TomTom software (no hardware unit) to replace the software that came with my GPS PDA. The difference between the "medion" software and the TomTom software is astounding
Route planning is quicker and easier; the interface works better with a big fat finger (the OEM software really needed the stylus because the buttons were so small - useless when in the car) , and the safety camera databases available online are quite handy.
I was planning to get a SDIO bluetooth card or a GPS enabled phone, and subscribe to the "Traffic" feature. It supposedly re-routes you around all the major jams on the fly, but I havn't heard many reviews of that function alone, and I'm not sure if it's worth it.