Have a Rider on my 999s, the mirror mount works great attached to the Olins steering damper mount. Been all the way to Luxembourg and as long as you get the europe wide maps, it makes the trip easy peasy !
Top tip is that you can set up a warning 'bong' to go off a set distance from a speed camera, mine is set fo 250m and is very useful...... :-)
One slight gripe is that the volume of the bluetooth headset is way too low, 100% is just about ok on fast trips.
I also have a TomTom installed on a PDA, which i used in a previous car, and thats pretty good too.
And for completeness i also have the factory satnav in an Alpina Roadster, which is a posh BMW Z4, and its nothing like as good as a tomtom !
So hope that all helps !