I've had an inexpensive TomTom for a few years now, and it's worked great. A couple of times I've missed a turn because I second guessed which turn it meant, and each time I knew immediately that I'd screwed up.
As for the iPhone, you might want to check with your provider...I have friends here in the states (on AT&T of course) who've been able to get international calling for a set amount of time while traveling in Europe, and it wasn't too absurdly expensive.
If you want to send me your Suhr/Axe FX rig you can borrow my iPhone while you're traveling...