DD doesnt' easily transfer from car to pram as she knows we are out and about so wants to look around!!
However coming home from car to cot she is really good. But only if she's just fallen asleep in the car in the last 15mins.... any longer than that than when i move her she wakes up and thinks she's had her sleep! lol very difficult timing it!!
I make sure her room is ready to go if we are out and i know we'll be coming home around the time she'll be sleep and then i take her straight upstairs and worry about the bags and closing the garage door etc later on..... we have a good little system in place now!
Sometimes she'll let out a little cry but it's only cos i'm moving her and she falls back asleep! The other day I left the radio on when we went out and that woke her up as i took her upstairs!! Doh!

Good luck! It's very tricky working out these babies at times!!