I replaced my TomTom 550 with the XT. I'm not thrilled about the map situation. I used the 550 in the US&Canada and Europe; all maps were part of the purchase. The XT only has North America; I'll have to buy Europe separately. Grumble, grumble...
The reason I dropped the 550 is simple. The POI searches were unreliable. I lost count on how many times I searched for something and got no results from the 550. I started checking the searches using the online TomTom POI using the planner app, and the searches resolved as expected. I spent much of the last two months laboring with TomTom support over this issue. Their "fix" was to tell me to write up a suggested map fix. In some cases, the searches were for businesses in place for 20+ years. Enough.
I used a Garmin 660 on two trips in the Alps, and particularly on the second trip, it failed spectacularly. And I have video to prove it (that's my 660 in middle of the K1600GT's dashboard). [/ grin]
There's the easy way over St. Gotthard Pass (see video open), and then there's the cobbled roadway that preceded it: "La Tremola".
I built a route, in BaseCamp, to get me from my hotel to the pass, and then onto La Tremola, going up, and coming back down. The 660 ignored the turn off the main road. I finally got on La Tremola on the way down (yea!), but at almost anything vaguely resembling a road, it tried to send me down that road. Exciting "detours" include a footpath(!), and the entrance to a Swiss military base(!!!).
I gritted it out with the 660, but finally said "I've had enough of Garmin". The TomTom started out OK, but somewhere in the last few months the wheels fell off. Updates should have cleared up any problems, but they made it worse, not better. Go figure.
So now I'm back to Garmin and the XT. My experiments to date have been successful, both for finding destinations the 550 can't, and for general routing. The 550, for example, has no idea about "route shaping". On cross-country, definite waypoints have to be created to favor one route over another.
I haven't tried building a route in the current BaseCamp, and feeding it to the XT to see what happens in real time. Watch this space...