My only complaint about using an ipod touch, since I have used my iPhone in my car(with a connection kit) is that it locks you out of the music player interface once the connection is made and forces you to use the car controls. I am not sure if all ipod connections do this, but mine did. Not that big a deal when I am driving, but if I passenger wants to browse through music and play stuff, its more of a hassle. There is a jailbreak app that fixes this, but I am not sure if the latest ipod touch has a jailbreak on iOs 5.
