I'm doing my research for a new car, which I've decided must have navigation as one of my "must have" features. I've not seen a comprehensive review of the various navigation systems. I've only read bits and pieces about the pros and cons of various systems, such as how just every journalist dislikes BMW's iDrive system, especially when its used in conjunction with the navigation system. I've read that Mazda's is also not that user-friendly and that Lexus and Infiniti's Birdview is very well thought of. Any other observations from real world users? Any input would be greatly appreciated!