I stumbled over Vodafone's Find & Go Sat Nav service when I was looking at the Vodafone Website, and I've got to ask, why would anyone ever use it?
For £5 a month you get turn by turn navigation - but dedicated GPS units can now be had for 50 - 60. It means 2 devices, but the dedicated GPS is probably going to be a better turn by turn navigation experience then your phone.
I use the GPS on my Nokia N95 8GB a lot (I prefer Google Maps over Nokia Maps, but both are free). I've never been in a position where turn by turn would be useful - while walking I just need to know where I am and where I'm going and the screen is too small to make it useful as an in-car GPS (that's what my Garmin nüvi 710 is for). If for some reason I do want directions on my N95, Google Maps can provide them.
So, like I said at the begining, why would anyone pay Vodafone £5 a month for Find & Go?