I'd look for one that you can plan a trip with waypoints rather than one that purely plots a route from A to B which the cheaper ones tend to do. Nice to sit down at a PC and plan a route to download to a sat nav but it's handy to be able to do it on the hoof away from one.
I've been on a number of European bike trips where I've seen guys carrying a laptop with them just to plan routes
I don't find much to choose between Garmin or TomTom. I currently use a Garmin Nuvi 2598 for the cars which has lifetime updates, has lane guidance which I find useful and a host of things I probably won't use. It's slim enough to fit in the Morgan without taking up space, unlike my old TomTom Rider which with its hefty cradle was just too bulky. And that's the problem with motorcycle satnavs...the bulky cradles.
In the Z4, I prefer to use CoPilot GPS on my iPhone which neatly sits in my ash tray!
PS. Just seen Adrian's post....he must have slipped it in whilst I was writing mine!
I was going to mention the mount but couldn't remember it's name! He showed it to me a few months ago and I've been meaning to get one...it is very neat and quite unobtrusive.
