This gave me a chuckle. We've had Sweep for four years, so she's very adjusted to home and pet life. My parents dog-sat her for the first time a couple of months ago. When I called to check in, my mom asked, "Is this really all she does?" Yep, pretty much! They're not called 45mph couch potatoes for nothing.
As others have said, Luna's very new and still adjusting. Her personality will come out more and more. It actually sounds like things are progressing really well. She's already learned the stairs, wags for you and follows you around, and might be displaying early signs of toy hoarding tendencies? (Sweep thinks that's the best thing about stuffies: pulling them out of the basket and taking them back to her bed.) I worried a lot in the early days too, and my adoption group said they loved the "paranoid android" adopters best, because they knew the dogs were going to be so well cared for.
Anyway, welcome to GT! We'd love to see pictures of your girl!