As of Feb 2008, Analog Cell Service will cease in most places:

http://news.com.com/2100-1039_3-6143866.html
"While most U.S. cities are blanketed with advanced cell phone service at least four times over, huge patches of rural America still don't have cell phone coverage. What's more, the problem could get worse before it gets better when rules requiring carriers to offer older, analog service expire early in 2008."


Effects include knocking out 10% of OnStar subscribers:
http://www.tmcnet.com/usubmit/2007/03/30/2454117.htm