Experience with mobile navs?

Ay Jungens, what experiences have you had with navigation systems that are not permanently installed? I have a change in my mind again, my old TomTom is ticking around a bit. Back then it was still new http://www.motorkultur.com/…/5533-they-have-reached their goal.html Or should I buy a good software right away for my mobile phone (HTC Magic with Internet Flat)? I am on the road quite a lot, because the normal Navi is actually mandatory, right? Questions about questions… Sandman