In the most important regard: useful routing, the 550 is simply unreliable here in Germany. Almost any road outside of a town or city has a (national) speed limit of 100 km/hr (60 MPH). For that reason, any attempt to pick a fast route over any distance results in being sent up routes that are simply not workable for fast travel. Either the route passes through town after town after town (national city and town speed limit is 50 km/hr or 30 MPH and it can often be 30 km/hr or 18 MPH - "blitzers" or speed cameras wait for the impatient), down county roads that are often 1 1/2 lanes and in miserable condition (yes, some German roads well and truly suck) as well as being used by tractors hauling... whatever, or all of the above. At best, it takes looking at a map to pick some intermediate points and/or heading for the nearest autobahn and hoping for the best. "Take me to the twisties" navigation is no better. In short, the routing function is painfully inadequate here.
And, truth be told, even in the States, the suggested routing can be rather bizarre, too.