Should I Get Nav?

[Tony0000]

Hi. I'm planning on buying a 135i. From looking at photos, I see that some have navigation and some sort of screen in the middle of the dashboard. My questions: How useful is a navigation system from maybe 2008 compared to using my cellphone? What else is displayed on that screen besides navigation? Can it be used for rear view camera install? And--bottom line--is it worth paying to get a 135i with one? (I had a 128i without one, just used my cellphone for nav, and did okay.)

Thanks!