TomTom's co-founder and CTO Peter-Frans Pauwels first demonstrated his company's turn-by-turn solution for the iPhone at WWDC in June of '09. You can watch a teaser video above. Since then, many customers have anticipated this app's release and pricing.
Handtec may have let the cat out of the bag. Daniweb linked to a page listing "TomTom for iPhone including mount" for £113.85 ($193.89US as of this writing) via preorder. That's a bit steeper that we were expecting here at TUAW, but not astronomical. TomTom's stand-alone units range in price from $119 to nearly $400. I hope to use my 3GS as a turn-by-turn device and avoid adding one more "thing" from the car.
How about you? Are you interested in an iPhone-based solution or do you want a stand-alone?