OK, I went to Onstar and watched the demo
http://www.onstar.com/us_english/jsp/plans/tbt.jsp
It seems interesting in that you never have to input to a screen. It's all spoken. $300/yr , but that would include all the Onstar services. Would I miss the pop-up screen? Don't know, it does look cool. Would save about $3,000 though. Once again, has anyone tried it?