I removed the crappy one that came with my car. I've held out on 3rd party solutions from Tom Tom, Sony, Garmin, and Navigon. I even refrained from a pretty decent solution for my Sony PSP because it doesn't have a touchscreen. My iPhone is with me 24/7 so it's about damn time somebody came up with a viable (no-hack required) solution.
Nav N Go demoed their iGo My Way 8 software on the iPhone and it seems perfect. I've used iGo on an old Nokia phone before so I'm familiar with the interface, not to mention satisfied with its GPS capabilities. The iPhone version utilizes a small dongle to receive the GPS single and that's about all you need to get it working. Best part is with the iPhone's multi-touchscreen, manipulating GPS data will be that much easier and fun!
Hit the jump for the video. Try HARD to ignore the awful elevator music.