Thanks, will not re-route while on the motorway then for the moment.
First real road test today, actually relying on it to get me to the UK Car PC meet, and it got me there!!!
Didn't crash once !!! Routing directions on this journey were just at the right time, and voice directions guided me home.
Only 1 bug... I planned the destination and drove there, for the way home I said 'Computer Take Me Home'. The bug appears to be if you ask it to re-route, it re-routes to the old destination. Also for some reason it tried to re-route half way home without asking it to which of course was confusing and needed to ask to be taken home again!!