I have been using my 2G in the G37 for almost 2 years now and i haven't had any problems with the phone. Just ignore the warning its apple's way of scaring you into buying some overpriced adapter from them.
Also the 2G charges the 3G and 3GS wont charge with the equipment that comes with the G37, which is really unfair. My friend had mentioned he had the same problem with his car (not an infiniti) so i am led to believe that apple tweaked the newer phones not to charge so you would go out and buy some overpriced adapter from them, lol.
As for the car menu for the iPod function, its really a little messy. I have about 900 songs in my iPhone and going through the song list is nearly impossible if the song i want to play starts with a letter in the middle or higher in the alphabet, you have to go through every song to get there.
Also it may be a glitch but if i click say genre - rock- artist - pick an album- then pick a song, then decide to pick another rock artist by backing out of the song screen it wont select the option, i basically have to go back to the iPod menu and reclick my option for another artist or album. Really annoying.
The 3.0 update actually improved the podcast function before i would have to fast forward the podcast to get to another part, its corrected to be broken up like individual tracks and you can skip between them.
Also for some reasons you can't sync the phonebook to the car, you have to manually enter your contacts.
Besides all that the car really is great, and the iPhone/iPod hook up plays well in terms of sound quality.
Enjoy and congrats on the G37 convertible!!