I can't comment on the Nuvi directly, although a few of my coworkers own one and have never talked of any problems with it. I own one of Garmin's StreetPilot series, and absolutely love the thing to death. I've had absolutely zero, as in nada, zip zilch problems with the thing. It works like a champ, and I think the company does a fantastic job standing behind their products. My one and only complaint about them is that at times the "Support" page on their web site seems to get caught in a loop regarding the "e-mail" option. When you choose to e-mail support instead of calling, it asks you to sign in. When you sign in, it takes you back to the screen where you can choose to e-mail support. Choosing that asks you to log in, etc. That's pretty easily resolved by calling, though. So I'd check with them. Google "Nuvi losing satellite connection". Call their support. Somewhere there's an explanation.
I always check mine on a point I've repeated many times which happens to be a local control monument with Lat and Long. Yes, I'm obsessed!!